Blimey, there are quite a few types aren’t there !
Unfortunately my van is down at the yard with the weather cap in place.
Can you read the towbar part number on the actual bar itself, and then check the link you gave, as it lists compatible towbars.
Otherwise, the cover part no may be on the part itself, in which case someone with a van closer by may be able to help.
My towbar part number is 321546, but yours may be different.
The picture posted shows the VW part number, which will be different to Westfalia’s.
I have a 3D Printer, and would be happy to print one - the risk that it doesn’t fit is minimal as the cost of plastic is trivial.
Just need to find a design that looks vaguely right !
Pete