You can use any brand re-chargable 2000mah or high and you have to peel off the plastic on the battery.
Theirs great places for this, they are mostly independent and with different names so I cant help their, but google battery shop near "your address or zip". If you find Battery+ then run their as fast as you can. That place is the s**t, cant beat em. If you find some other place then try them out also. Just tell them you need a nimh battery AA rechargeable, they'll have one. You shouldn't have much of a problem with the 2000mah but double check to avoid problems. Again, try and find Battery+, they always have what you need.