well ive used the same style, im a big fan of hydro farm gear, so i use there fans they work really well,just kinda noisy but not to bad on the price either.
you can see them at Hydrofarm - Grow Lights, Hydroponics and More! you cannot actually purchase anything from this site but its another site for you 2 look at and get a better idea of what you might be looking for in the future. they also have $50.00 fans that are probably a little more stable than the hd ones. same style and everything.also take a look at there squirrel cage fans they move a lot of cfm for little money...