Speaking from my field of expertise, which is Roman inscriptions, you do indeed see a large of names ending in -ix in the nominative case from the area of Roman Gaul and other areas with celtic languages. Inscriptions are a great source for questions such as this, since they preserve a large amount of names that we don't get from literary sources. This includes tombstones, votive inscriptions offered to certain deities, and importantly the marks left by the makers of pottery. For the Roman area, this allows us to gather a large amount of personal names for Gaul or Germany. Many people in these lands conquered by the Romans retained traditional names, for various reasons, and so we can still observe these names in the surviving material. Since the pre-Roman groups in these lands had different writing cultures that didn't produce such a large amount of names from different social strata, it's a very useful source for personal names of Celtic etymology. And among those, many do end in -rix (genitive -rigis/rigos). Rix (*rig-s) is 'king, ruler' and thus closely related to Latin rex, regis, and as a suffix found in a lot of names from those areas, and incidentally in a lot of Germanic names as well. So you have, f.e., famous ones known from literature such as Vertingetorix, Cingetorix, a ruler of the Treveri and ally of Caesar, Dumnorix, the brother of Diviciacus, or less famous ones such as Biturix, whose name is known from a large amount of pottery that bears the mark 'Biturix fecit', Biturix made it. Other common ones are Damniorix/Dannorix or Toutorix. Here's a list of Celtic personal names ending in -rix from Roman Britain.

In Galata, an area in modern turkey settled by celtic groups, you'll also find names ending in -rix, such as Zmertorix (ruler of Eumenia in Phrygia, installed by Marcus Antonius) or Albiorix.

Asterix itself has no parallel in the celtic onomastic material, but is a play on the name of the typographic sign *, the asterisk, the little star (an apt characterisation of the titular hero), same as Obelix on the obelus ÷, with both, as with the other inhabitans of the village, ending in -rix. Incidentally, for a few decades now (but not when Asterix was first created), we have proof for a personal name Obbelexxus, appearing on a stolen silver votive tablet from Aquitania recovered from the Rhine (probably lost when Germanic raiders were returning across the river). These latinized forms with the ending -us appended are another common feature were the '-ix' element appears.

If I may butt in someone else's question... What of the women's names (ending in -ine in the original french)? And do we have any such written traces?