vagcat is a website.
I think the only chance of getting a spare gear is to find a 2nd hand G40 box or put up some wanted ads, maybe someone has a spare but I'd not be too hopeful.
I'd give the whole box a rebuild and a good clean (clean all the parts in a parts washer), there will be pieces of that tooth knocking about all over and likely to cause more damage if you keep running it. VW might sell you a gear but last I heard of someone buying a gear from VW it was the wrong side of £150.