DIY Microtonal MIDI Controller... keyboard suggestions?

Hello folks,

I've been throwing this idea around for quite some time now, but I'd
like to come up with a design for a DIY MIDI controller. It seems like
it would be incredibly easy using something like the Arduino
Duemilanove, which is programmable in C/C++ and uses an AVR
microcontroller (http://www.arduino.cc). If you don't know about the
Arduino, and you know even a little bit of C or C++, you should
definitely check it out. It makes microcontroller programming
incredibly easy. And, it's fun! (tm)

The only thing holding me back from this is that I'm not sure what we
could use as a keyboard to do it. I'm only acquainted with the
Bosanquet and Fokker keyboard layouts, and so far I haven't found any
commonly available, cheap panel of buttons to cannibalize for this
project to match either layout. Does anyone have any ideas? I've
thrown around the idea of perhaps destroying a computer keyboard and
setting it up in some kind of pseudo-Bosanquet fashion but it seems
like a pretty lame option. Does anyone know of any products -
children's toys, perhaps - that have a large bunch of buttons laid out
in an array that would be suitable for such a purpose?

-Mike