This video shows how to put together the some-assembly-required MIDI-Fighter DJ controller.
MIDI-Fighter is a 16-button controller that features arcade-style switches. It's designed to be easy to customize and mod. It also features open-source firmware, so anyone can potentially add improvements.
Pricing and Availability
MIDI-Fighter is available now DIY kit for $125.
Link:
James LewinDevelopments for Korg's instrument have been slow but promising.