mobunny, you can get the smallest little speakers nowadays; should fit into the suitcase no problemo. After arriving, just hook them up to your discman, plug in with the adaptor and there ya go . . .tunes.
The speakers I used before (paired) took up about the same amount of room as a man's shaving kit. But just last week, I found some speakers that were shaped a bit like an L-bracket. They were totally flat, otherwise. They were also reasonably inexpensive and would probably fit neatly into the corners of my bag without taking the place of anything else at all. And so of course, I *must* have them.