Also if you completely discharge the batteries, they will "come back to life" for a little while. It won't fix the problem but helps somewhat.
and I mean completely discharge them. you have to drain as close to all current from them as possible (don't just short it though that will damage them, you need a slow constant drain)
Well any rechargeable battery should work, because i use a variaty of rechargeables with a different brand charger. But if you can't afford to buy some, try making sure they waste all the battery, then recharge it, if it doesn't work then sorry i can't help you more.