I'll have to dig mine up but I think any standard 9V adapter from Radio Shack works well. Amperage is one of those things that systems only pull as much as they need. It's part of OHM's law in elelctronics. :)
You can also check how many amps a "D" size battery outputs and then mutiply that by 4 to get the total amount needed -- they worked on that as well.
