Just musing aloud here.
Dunno who makes it, but it was used in Dream Machine '05....they make a keyboard with blank keys. No letters, numbers, NOTHING. What about picking up one of those, removing the casing from it, and setting the whole thing into a piece of cherry. Dunno if you need actual keyboard usage, or if you simply want to customize a few keys here and there, but you could make it so the top of the cherry slab is even with the keys, as if you're pushing IN each button, rather than having it like a keyboard. The blank keys would allow you to set up each button for whatever you need it for, and you could label them whatever you wanted, say a one-button macro for XM would have the button labeled (duh!) "XM".
Just seeing what sticks.