ORIGINAL: ProBroJoe
Or... you could just buy an el-cheapo brushed speed controller and use the BEC circuit there...
http://www.bphobbies.com/view.asp?id...8&pid=NESKY159
There are physically smaller ESCs, but I like that this one claims a 1.5A BEC circuit - should power just about any 1/2A model with overhead to spare.
Be careful with this approach, ESC's (especially cheap ones) can't handle large numbers of servos. The current draw ends up being too much-ChiCom servos in particular are a problem as they use hot motors in their servos to get the transition speeds up. It's the startup current the motors pull that is hard on the BEC.
Three servos is asking as much as you can from a typical small ESC.