I purchased a Bluetooth Car Radio from Aliexpress and powered it using both a power bank and solar unit. The latter in particular, proved very useful for camping when you can't charge your batteries. It has a number of modes including radio, sd card, ancillary port for say usb and even a hands free Bluetooth mode. The whole unit, including postage, sets you back about 4 dollars.

Supplies

Car Radio

To power the unit - either

a) Solar panel - delivering between 5 and 12 volts ( you may need to regulate higher voltages with say a L7805 voltage regulator)

b) Power bank delivering at least 5 volts

An old speaker ( I used both one from a pair of PoundLand speakers)

An aerial - For expediency, I unashamedly used a Dupont cable connected to a Crocodile clip pair

Cable connectors ( see image - e.g. Self Locking Electrical Cable Connectors Quick Splice Lock Wire Terminal)

An old micro-usb connector which you cut and plug the thick end into the power bank / solar unit.

Step 1: Assembling the Device

The assembly is quite simple.

Connect the speaker connectors on the radio to the speaker ( +to +, - to -). I was able to get a reasonable sound ( see video) without amplification.

Choose a power bank or solar panel to power the unit. The range is 5 to 12 volts. I selected power sources close to 5 volts. I also cut up an old usb cable and using the large end, I spliced the wires to make a connector.

Use cable connectors for expediency and a good connection. Later, these can be made permanent using shrink tubing.

Set up the aerial using a Dupont cable connected to a crocodile clip cable. Again, this works, but later I will make a permanent fixture.