I see that the AMRAM2 used the 40LF220 SAFT Memoguard 3.0V Lithium Encapsulated Cell battery which is now hard to find (or generally about £20 for a battery).
Someone has developed a replacement low profile holder which takes a CR2032 lithium battery - it is designed for use with the Sinclair QL's Super Gold Card which also needed a low profile replacement.
http://www.sellmyretro.com/offer/details/GoldCard~~Supergoldcard-Battery-Replacement-10926 (http://www.sellmyretro.com/offer/details/GoldCard~~Supergoldcard-Battery-Replacement-10926)
I don't have a AMRAM2, but I have bought some of these for my QL computers. Paul, the seller is super quick with dispatch. So recommended by me.
Mark
I have one, but it's too late because I already made my own version, it's not as nice, some wires, a CR2032 holder and some tape to stop it shorting on the board above :D
I think I must be almost the only person to have one of these amram2's.