i just picked up 2 HItec HSR-1425cr servos from Hobby horse for about 17.00 EA + shipping. They are continues rotation so they don't have to be modified to be used as wheel motors(if that is what you were going to do with them).
The specs on the package are :
Operating voltage : 4.8 to 6.0 v
Operating speed : 43.4 rpm+10%
Output torque: 38.88oz-in
***I in no way have any affiliation with the hobby shop mentioned above ***