Here's the Hiwatt one on MF
http://www.musiciansfriend.com/srs7/...se_pid/801177/
I think making use of an A/B box of sorts to go to the theremin in a stomp would be cool. Like have your guitar signal come into the box, and then a lead from the theremin going to the other jack, and that way you're running it through all the pedals, and such, and you can switch back and forth with no need to have two amps, or take your guitar off.
.chris