I had earlier a post on finding compatible battery replacement. Koonlung's apparently out of business.
Now I need to find a way to make its car adapter work. I was able to disassemble the adapter to find a broken piece inside. I attempted to solder it but failed. At this point, I'm looking to buy a spare adapter that's as simple as this one to swap heads with it. I would have to bring this old one to shop to find a matching head.
Update 1/14/2023: Bought a USB car charger ($6) from Five Below at the Freehold Raceway Mall. Looks like I would have to do some swapping of components with the old one to fix this. First, I needed to learn how to remove component from PCB, the conventional way (no desoldering gun, etc.)
This was done, but without the modern desoldering method, the PCB was left with messy tin covering the holes where components were removed. So it's probably time to pursue my long desired (since high school) project: Learning how to create PCB board. Apparently there are companies that will take your circuit design order and ship you the corresponding PCB:
Or you can create it yourself: