Have you considered one of those new "Bass Boxes" ??

Mudcatter Allan C. has one and sent me a site URL, but not being at home I can't supply it now. If no one has chimed in by the time I get home tonight, I'll post it.

I haven't heard a Bass Box yet, but the descriptions say it sounds much like an acoustic upright bass. From the pictures it's a well made wooden box (about the size of a big breadbox) that you can sit on to play - has five finger-like keys that you pluck with one hand (like an overgrown African "hand piano") while the other is free "to drink beer."

It is apparently somewhat tuneable and will accomodate the keys of C, D, A & G, as I remember. The Bass Box runs about $250 US, plus shipping.