amazon has several rechargeable ones.
I used one while I was building my cabin and didn't have my shower setup yet.
I think I paid about $25 for it.
I'd give you a link but I don't think it's the same anymore, you know how these cheap electronics companies are.
Mine is similar to one like this:
https://www.amazon.com/RISEPRO-Portable-Rechargeable-Charging-Cleaning/dp/B07CZFQZQM/ref=sr_1_5?crid=XFW3O1H4UF1U&keywords=rechargeable+shower&qid=1678907432&sprefix=rechargable+shower%2Caps%2C222&sr=8-5