We have been buying the 3Racing heatsink/fan combo from a person on Ebay out in the Washington area. They are like 6 bucks and he ships very fast.
What we do is take the fan off, flip it upside down and mount it using only the 2 outer screw holes to it hangs over the side. Basically you are left with a heatsink on the motor that doesn't restrict a lot of outgoing air flow and a fan blowing directly into the endbell. For 6 bucks it actually does work. With this setup we usually break the fans pretty quickly in a side impact (doesn't take much) but the fans are available seperately from the same guy on Ebay for like 3 bucks. We just grab them 2-3 at a time =)
Have fun,
Nick