Mad Catz Rock Band 3 w/ MIDI Keyboard [xbox 360] $39.99 + FSSS!!
 

• Game Software Included
• All-new Keyboard instrument for Rock Band 3 / Plays Rock Band 3 Keyboard, Guitar* and Bass* parts (*Does not support Guitar / Bass Pro Mode)
• Two-octave design with 25 velocity-sensitive keys / Play real Keyboard parts in the new Rock Band Pro Mode
• Versatile layout: Play like a Guitar or on a tabletop / 3 AA Batteries and Keyboard Strap included
• Use as MIDI Keyboard Controller when not playing Rock Band (compatible with most MIDI sequencers)

Linky [amazon.com]

Thanks OP, but please put XBOX 360 in the title (or somewhere in your first post).

I was hoping for the PS3 version, but it seems to be OOS everywhere :(

yw and added :)