Hi Pete,
Yes some sellers are definitely a rip-off. The screws are almost ordinary M6 countersunk socket heads, as sold by a well known online supplier, product code 96477. However, I say almost as they are slightly longer than the originals (16mm as opposed to 10mm but shouldn't be a problem to anyone with a hacksaw or bench grinder) and, more problematic, the head is slightly larger than the originals. That isn't a problem for most of the jaws, but if you need to you can file/grind the heads so they can be inserted into the holes on the jaws. The good news is the current price is £2.65 for a bag of 50, and they are stainless steel. I would offer to post you some but at that price, I am sure it is easier to get them from your local 'fixer'.
Hope that helps,