NEED HELP ASAP

OK, this may seem weird.

I brought a catalic converter from GSF for my Audi 80 2ltr 16v but the olive/silencing ring from my car does not fit the new cat, i cannot find an olive/silencing ring any where that is 6.5 cm across.
The one i have from my car is 6 3/4.

Audi themselves say they would only sell me what i already have.

GSF say go to AUDI.

My mates cant find a thing either from where thay work.

Has anyone else had this problem.

The downpipe is an original Audi part.

NEW CAT

OLD CAT

So weird.

Well i have brought another cat and the olive fits this cat, BUT this cat is 1.5 inch shorter than the origianal. ?????????