Here is a simple little modification I did to my Kenwood TK2100 MURS portables from the $49 MURS Radio place:

Works great since most of the needed circuitry is already inside the drop in charger!

 - Pick up a small solar panel. I bought a small folding 5W solar charger from Northern Tool. Unfortunately, it is no longer available. Pretty much any panel greater than 5W will work well.

- Next, I picked up a couple of extra chargers from the $49 MURS Radio place. They often has unadvertised extra parts at decent prices.

 Construction is simple. I took the cable from the charger's power supplies and cut it about 3-4 inches from the power cube. I left some wire in case I ever wanted to use the power cube for something else. I then took the wire from the cable with the white stripe and connected that to the positive connection on the solar panel. Then take the other wire without the white stripe and connect that to the negative side of the solar panel. You could even put your own connectors on these cables so that you can switch back and forth between the panel and the power cubes.

The stock chargers have a voltage regulator in them so a charge controller is not necessary. You can take the voltage straight off the panel.  You could also substitute a cigarette lighter plug for the solar panel and charge these radios off your vehicle's 12v accessory outlet.

Since my panel puts out 5W in maximum sunlight, here are my calculations on charge time:

5W is about 300 mA at full panel output (~16v)  in full sun. This will give you approximately 250 mA at 13.8v which is close to the power cube's output. Dividing this by two, if you are charging two radios at the same time and you'll need about 16 hours of full sun to fully charge the batteries.

Since the charger bases also have a current limiting circuit to protect the batteries from overcharging, you can essentially hook your chargers up the panel and keep them charged up for whenever you need them.