There are indeed some sites that offer 6 max tables in MTT format (not just SNG/cashgames). I'll do a little looking around and post back here with some of the sites.
Kenzie was right about the Titan MTT 6 max tables, they do run a few of those a day with a guaranteed prizepool.
Add PokerRoom.com to the list. Just saw a short-handed $20 buy-in MTT.
You can also find one at PokerStars
Actually, short-handed games are pretty popular, so with a little searching, you could probably find MTTs in this format at quite a few sites.