Either of these should fit what you've described:
http://www.performancebike.com/shop/...tegory_ID=5240 - smarty $34.99
http://www.performancebike.com/shop/...tegory_ID=5240 - eggbeater C $49.99
I used the eggbeater C's for several years on my mtn bike (still do on the road bike.)
The only problem I had is that if you ride in really rocky terrain and tend to slam the pedals into rocks really hard, you can break a wing occasionally. CB seems to have no problem warrantying them. And if you don't do stuff like that regularly, it's not an issue. I'm the only one I know who's had the issue.
I'm now on the Eggbeater SL's on my mtn bike, with no issue so far