It can be a little tricky, but if you know what the adapter is rated to handle it usually isn't too tough to find one that works. About 5 years ago I ordered s

It can be a little tricky, but if you know what the adapter is rated to handle it usually isn't too tough to find one that works. About 5 years ago I ordered some 4-port 2.1A Monoprice PoS adapters for a few bucks a piece. I routinely use these for my RPis, but with only one RPi plugged in (add any second device and the thing will start flaking).