They're probably SMPS which can be time consuming to fault find and repair, and not always possible to get certain spare parts for.
If you look at the usual suspects - CPC, RS components etc, you should be able to buy a suitable charger for a lot less than that. You'll need to ascertain what type of batteries they use. SLA types need a different charger from 'wet' lead acid.
You'll probably need to have the correct output plug fitted. A neighbour's one uses an ordinary 3 pin XLR connector as used for microphones.