I don't know the answer to this, but one major problem is that we don't have many literary sources from outside of Greece and the Roman Empire, especially in Europe (we do have a decent amount of records from Persia and the Near East; there are some Hebrews who could count as philosophers, albeit with a Hellenistic influence, as well as some Persians and Mesopotamians, but these seem outside the scope of your question). Many cultures outside of Greece and Rome were pre-literate; and from those that had writing, few accounts survive, due to a variety of factors in manuscript tradition. In one notable example, our best source for the practices of druids is actually Caesar. So, even if there were barbarian philosophers, we likely wouldn't know about them, due to the lack of sources.

By tradition, the Orphic mysteries were Thracian and were imported into Greece during the classical period. In its teachings about an immortal soul, resurrection and a rather immanent sense of the divine it may have been highly influential in Greek religious life, and at least was quite well known, being mentioned in Plato several times. The problem, naturally, is that it is very hard to know whether it was actually Thracian or if the Greeks (more precisely, the Athenians) simply said it was because, as they often did with their little cultural bits and bobs that didn't seem to "fit", it was easy to connect oddity with foreignness. Bacchic mysteries, for example, were frequently thought to have been imports from Asia Minor, but we know that Dionysus was worshiped back during the Mycenaean period.

The druids of Gaul, at least at an early stage, seem to have been considered as barbarian natural philosophers by the Greeks and Romans. This is significant because those who mention druids in such a capacity were often philosophers themselves, showing that classical thinkers recognized them as fellow-philosophers. Unfortunately, we have no direct sources regarding their teachings, however classical texts mention some of their beliefs: they believed in the transmigration of the soul after death which was compared to Pythagoreanism and apparently had a sophisticated understanding of the cosmos. In Ireland the druids seem to have been more concerned with the workings of the cosmos and its potential to cause celestial portents than the continental druids' intricate philosophical/religious teachings, showing that the druids weren't a uniform entity and had important regional variations.

However, after the Roman conquest of Gaul, the druids' social role evidently collapsed and lost their prestige and sophistication. Later references to Gallic druids almost always refer to them as magicians, conjurers or healers; they had lost their intellectual dimension and been reduced to the status of 'cunning men'.

To clarify, by barbarian I'm talking about anyone who wasn't Greek or Roman.

This seems more specific than what you intend to ask. I doubt many would call the various Chinese dynasties "barbarians". Perhaps you mean philosophers from the less literate or more tribal civilizations which still can lead to some arbitrary distinctions.

If Anacharsis is the kind of model you're looking for, probably the best other example is Zalmoxis. According to Herodotos 4.94-5, he was a slave of Pythagoras who, when he was freed, went off to start a cult in Thrace (modern Bulgaria/NE Greece) and "became a god". The same material gets repeated in Strabo 7.3.5. The entry on Zalmoxis in the Souda (a 10th century Byzantine encyclopaedia) makes him Scythian or Hyperborean (modern Ukraine) rather than Thracian. Another Souda entry suggests that he may have been equated with Kronos in some circles.

Herodotos' story could mean either that (1) he was a mystic who came to be worshipped as a god; or (2) "Zalmoxis" was a Thracian god, and the backstory about him being Pythagoras' freedman was a post hoc invention to rationalise him. People often seem to take the second possibility for granted, because Herodotos talks about him as a god first, and then tells us the Pythagorean back-story; Strabo opts for the first one.

The Pythagorean link isn't limited to just the story of him being a slave:

• Herodotos and Strabo also tell us that he built a cave in which he gave his teachings -- something that Pythagoras also supposedly did, on the principle that that was the most fitting place for revealing mysteries.

• And there's a fragmentary reference in the scholia on Gregory of Nazianzos, which you won't find in translation I'm afraid, that links "Salmoxis" to another mystic from Hyperborea/Scythia, Abaris --

"Salmoxis who fires arrows in a swarm." This is Abaris of Hyperborea. This Abaris, as Herodotos says, came from the Hyperboreans. ...

Unfortunately there's no clue in the context of this note as to why the writer even mentions Zalmoxis. On the face of it the text states that Salmoxis and Abaris are one and the same. The phrase "who fires arrows in a swarm" looks likely to be a quotation from a poem, probably one attributed to Abaris, who was a legendary figure, supposedly a priest of "Hyperborean Apollo", who came to Greece and became an itinerant soothsayer, and composed five poems in Greek. In reality, "Abaris" is presumably just a fictive backstory for these poems, which were real literary works.

So there's yet another possibility, that "Zalmoxis" was given as an alternate name for "Hyperborean Apollo" in one of the Abaris poems. (Abaris was also known to Herodotos; and according to Iamblichos' Life of Pythagoras, Abaris is the one who identified Pythagoras as an avatar of Hyperborean Apollo.)

There isn't really enough here to show decisively that Zalmoxis was a real, historical individual; conversely, there isn't enough to show he was fictional either. But that's similar to the Anacharsis situation: Herodotos points out that he didn't manage to discover any evidence of Anacharsis in his travels in Scythia, and in later times Anacharsis was just a useful backstory for various pamphlets on Cynical philosophy that date to the 3rd century BCE or thereabouts.

Aside from them, we've also got magoi popping up in Greece here and there. Like Zalmoxis and Pythagoras, these were more religious figures than philosophers: they acted as the hierophants or gurus in various mystic cults associated with Orphism. Most magoi seem to have been Greek, but the term is a Persian one and conveys a sense of borrowing from eastern religious practices. Some of these gurus engaged with philosophy as a theology for their religious teachings: for example, one fragmentary tract by a magos, known as the Derveni papyrus, outlines a theology that borrows heavily from the natural philosophy of Anaxagoras and Herakleitos.

Didn't Herodotus claim that Greek learning in general came from the Egyptians?

Iamblichus, a Neoplatonist philosopher, was a Syrian. His name is even a native Syrian name, 'Imablichus' being a Hellenized variation of it used by the Greeks in their own writing (the original being something like 'Yamlikel' or 'Yamilku').

Philo of Alexandria was a Jewish Platonist.