I'd really like to find a rechargable 9V option too, im mostly interested in this as a curiosity than a true solution. I've had 'hit and miss' results with 9V+USB power, im no expert but I feel like the step-up converters are the issue. (Ive used an off-brand 5v-9v converter). Does Birdcord make a higher amperage cable (more like 1.5 or 2A)? I think the 9V1A output is at the bottom limit of the Stomp needs. IIRC, the HXS spikes at 1.2A at startup and then runs at 900mA, so a 9V2A output might provide solid continuous power. Again, just looking for solutions yourself.