Vortex Sound Research

I have the PO-35 Speak, and I love how you can record voice into it (via the mic or line in) and then apply various voice-specific effects, like autotune/robot/fifth, changing the formant, etc.

What I don't like so much is its reliance on batteries (seems like I'm always having to change them) and its dinky little buttons.

Does anyone know of a similar piece of kit that doesn't need batteries, has decent-sized buttons, and maybe even has MIDI in? I'm not talking about general-purpose samplers here, I mean hardware devices built specifically for synthesising and modifying voice, like the Speak, but less toy-like in construction.