Not sure if this is the right question for this type of forum, but I know Bose makes such a system, rumored to be 50-60 watts.
or something with more wattage (75), cheaper, but only speakers:
For my poolside (outdoor 25 meter pool) fitness classes I use a Hisonic HS120 B PA system. It weighs 6 lbs. and has a rechargable lithium battery and power cord. It comes with a few different mics, a hand held, a clip on, and a around the head style. They plug into the body pack which has a clip, but I often just put it in my pocket. It is very light and small. The sound is very good. I think it costs about $120 on Amazon. I like the very light weight of it. There are other options, I am pretty sure the one that I have is VHF, but there is bluetooth available as well.