Use case is a off grid Museum self guided tour. One idea is to set them up around a ghost town so people can tune in and hear a bit of its history and stories.
I have successfully used the Raspberry Pi transmitter and solar battery as a proof of concept, and have found kits [0] and parts [1] that can be pieced together. I do well enough to produce a prototype but lack the skills to create something that would stand the test of time.
Where would you all recommend to get something like this created? Also it’s important to me to keep it as open source as possible.
[0] https://learn.adafruit.com/minty-mp3/hardware [1] https://www.adafruit.com/product/1958
In other words, the playback device, transmitter, battery, solar charger, and solar panel can all be different parts. These days it's common to get the battery and charger together in one unit. But the rest of things tend to evolve separately and you can get much better quality for a given price by separating them than by trying to find an all in one setup (which wouldn't have the square area to charge a good sized battery anyway). If you want a few days of autonomy through low sun periods, it's really the battery that's doing the job, not the solar panel so much.
Or if it's for a self guided tour, can't the visitors provide their own smartphones? All you'd need to provide is an app with geofencing or QR codes or even signs labeling the stops.
Am I missing your point?