Oh, I DO have tons of working adapters that I can use for this kind of stuff. We save stuff here in Serbia. Whenever you get a new electronic device you get some kind of power supply with it. Device dies, power supply continues its life connected to something else.
I thought you might have some power supplies piled up. My comment was more of a reply to BassmanPaul than advice to you. I'll admit I went into more detail which I thought you or someone with similar intent might benefit from. It does sound like you have this mostly figured out. I'm still concerned that you might not get the best volume from this since it sounds like there might be a mismatch between the guitar output and the amplifier input. I doubt you'll damage anything, and you might be happy with the result, I'm just thinking it might be less than optimal. If it works for you though then that's all that matters.