If you make your way to a model shop that deals in Radio Control Models, you will be amazed at the various chargers / NiCd items you can find ......
12V in, 4.8 / 9.6V out, 500mAh, 250mAh etc. etc...... even a Battery Backer which connects 2 packs to one item and auto switches from one to the other when first is discharged - without the item knowing anything about it .....
I have a 12V input, dual output charger, from a Radio Control Outfit, that charges my HandHeld VHF ..... it is designed for overnight charging and does not 'cook' the battery, like most HH 12V leads .....
You will have to fit a suitable plug onto whatever you buy, but believe me they are good and designed to look after expensive flying Pride and Joy's. Just make sure you explain fully / or take in the item to charge, to the shop and I'm sure they'll come up with the goods.
(Note this is one of the best sources of Tagged NiCd battery's .... used to solder together in packs and replace various NiCd battery packs on VHF's etc.)