Probably one of the last versions of the TS22A manufactured by Harris before they sold the rights to Fluke. I've been looking for a replacement for that battery with no luck. Assemblies like that are custom made and since Harris no longer makes the TS22s you won't get any from them.
You might try giving
THESE guys a call. If they won't sell you a battery it would be worth it to send it to them for repair. That butt set is a lot newer than the ones I use.
Good luck!
-Hal