I havent seen any i just had a pipe welded in its place.

This ^

http://www.roadraceengineering.com/eclexhaust.htm

However, being that the cat-eliminating downpipes are much cheaper, your best bet would be to cut off a section between the hangers and the flange and put in a 3" cat (I'm assuming that's why your looking for one that doesn't eliminate the cat).

Why not just a cutout upstream of the cat if your set on keeping it?

Personally seems counter productive to spend good money on a few feet of 3" pipe pre-fabbed only to leave drinking straw attached to the outlet.