I like the hydro filters. http://www.jehmco.com/html/hydro-sponge_filters.html They take a good few weeks in my shrimp tanks before they need cleaning. You can put a small piece of a tube and small airstone in the bottom of them to get a nice fine bubbling coming from them.
The Hydro filters are kind of large for in-tank use but they work super-well.
My favorite are the double sponge filters you can find on eBay. Usually they range in price from $1 to $4. I particularly like them because you can rinse one sponge out one week and the other the next without any real risk of nixing essential bacteria (and the crunchies all my shrimplets enjoy).
I think you'd be fine with one of them because the lift tube creates a decent amount of flow.
They're just a couple bucks on eBay so maybe you could snatch up two and use them at the same time? Would guarantee your water stays super-clear and you always have some backup sponges in case you or a friend want to seed a new tank. ANd you'll have tons of flow from even the cheapest air pump.