sigma sn30 alarm advise please

[NeilH]

Could not find a more suitable forum to post in.. but I need a little help.

I have an old Sigma SN30 alarm siren in my car which has a backup battery installed.
This backup battery has finally died, and so it needs replacing.

Can this old siren be replaced by a more up to data version from the sigma range ?
If yes, will the alarm the need reprogramming ?
Having taken the siren apart and found the battery part no. anyone changed just the battery and where did you source the battery...a web surf has failed to find a battery based on the part no.

Advice appreciated...