| br>Good solution for speaker: Bosch PB360. It's a jobsite radio, plenty loud, and will run off Bosch tool battery. If there is a power lead, it will act as a powerstrip.
A KORG Kross will run off batteries, and run well. So will Volcas. The Casio XW-P1 will run off batteries as well. Boutique synths will run off batteries, and you can get a passive mixer to do that if you need it. Or the Behringer battery-operated mixer. Also, you can get a battery pack to run a few small effects or synths if you need them. The Zoom G1on is a great multi-effects DSP pedal that runs on batteries, and plays nicely with line level sources. br> br>