They are probably accurate. We can be as confident in these reconstructions as pretty much any other garment from this time period.

The garment (sometimes called a warrior jacket or, in German, a klappenrock) is frequently depicted in Vendel-period artwork, most prominently the foil pressblech plates that decorated helmets found at Sutton Hoo (England), the Staffordshire Hoard, and Swedish princely graves like those at Vasgärde. Here is an example from Sutton Hoo (an image also found in the Staffordshire Hoard). Here's another. And another.

Archaeological remains of garments from this period are extremely rare -- most of what survives are only tiny fragments in graves that rusted onto metal belt buckles. However, there are a few graves in England (6th/7th century) where the tablet-woven border of a garment with an opening in the middle -- probably the garment in question -- survives on the back of the buckle at the waist. Two of these English garments were made from wool; one was from linen.

Gold brocade has also been found in a few English braids, probably from the trim around the neck opening on one of these coats. You find this in the Tapplow barrow and in the chamber grave of the Prittlewell 'prince', both 7th century. These graves were full of lots of treasure, and were probably very important persons (archaeologists often call these sorts of burials 'princely graves', though we don't know the actual identity of the persons). We don't know the type of fabric from which these jackets were made -- only the gold wire that was woven into the trim survived. Odds are they were wool like the two I mentioned in the paragraph above, which is how the Wulfheodenas reenactors (the guys in your second and third pictures) have chosen to recreate the garments.

There is also a fragment of a garment, found in the harbor at Haithabu (Germany), that has been interpreted as part of the same kind of garment (this one is a few centuries later -- maybe the 9th). I believe this one was wool, though I don't have a copy of the book to hand to check right now (Hägg, Die Textilfunde aus dem Hafen von Haithabu, 1984).

This is not much to go on, but it's actually stronger evidence for the garment's existence than we have for most other kinds of clothing we know were worn in the Vendel period (like tunics and trousers). Archaeologists are, therefore, pretty comfortable affirming that the garment depicted in the pressblech art was probably real.

Penelope Walton Rogers has a good discussion of the different sources of surviving evidence in her book, Cloth and Clothing in Early Anglo-Saxon England, AD 450-700 (2007), if your library can track down a copy.