Solar/Battery Mini Speaker

Hi I tried to search and cannot find anyone with a project similar who posted parts.

Im looking to make a small solar charging battery powered speaker for my bathroom while showering. It only needs to run about 15 minutes a day, but it needs a battery so it can run when its dark out.

Im having trouble finding out which parts will be compatible as I have never tried throwing a battery into a solar panel mix. I'm looking for anything above cell phone quality/volume basically.. and it should be do-able!

I am looking to have:

-an amp - likely class D 2x3w stereo
-a solar panel - something around 5v - probably 0.5 watts
-2 small speakers full range.. probably 2.5-3"
-Battery pack - probably 5.5v (USB voltage)
-Any other parts for preventing current backflow or changing voltage?
-On/Off switch

So far Im finding bits and pieces but nothing is of use until I know which voltage im going to run at and I cant figure that out until I find whatever parts are needed between panel/batteries and batteries/power switch.

Any ideas on where to begin? I figured its similar to how those solar garden lights can charge a battery then run off of it, but those are such a low voltage I cannot just wire a bunch together.