I have a Zen Stone Plus mp3 player with its own built in speaker. The sound quality & functionality aren't the greatest, but I got it for pretty cheap on ebay along with a rubberized skin that attaches to a lanyard, so it works well for its purpose.

I haven't done many long solo rides in remote areas in ages, but I'll be putting it to use again soon.

No worries Lisa, I won't be playing it around you.