@budgiebin@snouts.online I was about to ask for measurements; I was able to find a part number in the service manual (the power plug is not proprietary, it's an HEC2305-01-030) but I couldn't find any actual datasheet for that
But if you want to modify it putting a new power plug in would probably be easy
Don't expect it to be all that energy efficient! it doesn't seem to be designed to run on batteries
@budgiebin@snouts.online oh I see the problem, it uses a center-negative input, which is opposite polarity from most of these things. The ones you plugged into it might have been center-positive supplies, which are more common by far (you can convert one by just cutting the wire and swapping them though)