The Fliper DJ a great MIDI controller, which also comes in its assembled version. It is based in the Arduino platform and contains 16 arcade buttons, 7 rotary potentiometers and 3 slider potentiometers.
One of the potentiometers allows you to change the midi channel of the buttons, making it possible to have four banks of buttons, 16x4.
The Fliper DJ is a USB-Midi class compliant device, no drivers or converters needed.
You can choose the colors of the buttons and the knobs.
All the code is open source, so yu can modify however you want.
You can engrave your logo for an extra $10.
*Because this is an "on demand" product, it can take 1 up to 3 weeks, if a component is out of stock.
For more info: firstname.lastname@example.org