Have you tried this Bluetooth Outdoor Speaker w/LED Light

Some small stuff may surprise you. I goof around with all kinds of audio stuff, mostly higher end hi-fi, but I do build smaller stuff. I have a small boombox I'm working on now. I've auditioned the speakers in small test boxes and the results were really good. Since space is a big part of the design criteria (mounting this small aluminum case on a bike), they had to be small. This is my current speaker of choice: Faital Pro 3FE20. This little guy is waterproof and plays 100hz to 20khz and does it well.