MIDI Controllers

I wanna hook up a MIDI Controller to my MPC 4000 so that I can play my Keygroups easier than on the pads. What's a good, cheap MIDI controller and how much will I be needing to spend? Any help would be greatly appreciated.

s/h the roland PC200 are very solid and do the job nicely (4oct good feel, economical in size, one data slider, the keys work as shortcuts to setting up MIDI and it just works no hassel included, 50-100 bucks s/h there's a MK2 dunno on how much better it is but yhea inexspensif and reliable..

new, I belive Alesis is bringing out some compact intercatif midi keys around 200-300 depending on size, looks like a good choice aswell..