http://www.full-race.com/catal...d=231
Here's what I did. Step 1 - Google "3 bolt downpipe flange." Step 2 - Click on first link. Step 3 - copy and paste.
If that's not what you want or the size you need, there are plenty of other search results that might be what you are looking for.
Just buy the flange and take it to an exhaust shop. Tell them you need a downpipe made. Either that or buy a pre-fabbed downpipe, cut the flange off and weld that flange on. It's really not that complicated.