I've never busked with amplification, but I think a small travel electric guitar (like the Earlwine [sp?]) and a small amp could pack smaller than a flattop guitar, making it easier to get around. Combined weight might not even be more once a case is figured into the equation. Personally though, there's something more pure about an acoustic and busking, but that's just me. Whatever works will do.

There sure are some real pro buskers!

Peace, Mooh.