Here's one option - not ideal but it's small, bus-powered, etc.
http://gamingmouse.com/weapon.php?pid=30
If you want to use plain old 1/4" out switches and pedals, you can use products like this to convert to MIDI:
http://www.midisolutions.com/prodped.htm
If you decide to go DIY there's some info on the solutions I've worked up, here:
http://www.decrementia.com/Content.asp?pg=Geek%20stuff
And I definitely advise doing forum search for "floorboard", "footswitch", etc. There are no ideal products on the market right now IMO (and to my amazement) but there are alot of approaches if you get creative.