I don't see where anyone suggested the Ray Samuel's SR-71A which uses 2 (yes 2) 9volt batteries. I enjoy both the SR-71A and the Stepdance but as everyone knows, the battery in the Stepdance does not last very long before it is exhausted. The SR-71A on the other hand lasts a good long while.
A second for the SR-71. It is a good quality amp and has done well against many others over the years.