Hi,
Just a note to say that it is perfectly possible to rebuild a battery from these compaq handhelds.
New Heatshrink tubing =
Tagged AF batteries =
https://www.batteriesplus.co.uk/acatalog/AF-or-A-Size-NiMH-Battery-1254.html
You need to use AF battery, as AA is just that little bit too long.
1. Cut open the old pack.
2. Disconnect the batteries.
3. Solder the new batteries together into series.
4. Solder negative terminal.
5. Fold the positive terminal to form enough of a 'bump' that it will compress onto the battery-pack connector.
6. Clamp everything tightly, and shrink the heat shrink onto the pack.
7. It will 'just' fit into the battery compartment