I can't help you with your question on repairing the corrosion. Fortunately, in my 33C and 34C the contact board is still in good shape.
I use AA NiMHs. I complete the circuit on one end with a bit of aluminum foil taped in place, and tape the cells together with a bit of packing tape. I then gently ease the exposed end of the new "pack" into the calculator up against the connectors (remember the positive end is bottom, negative top), and gently ease the other end into the battery compartment--since the positive end buttons on the batteries add some length compared to the original Spice pack, the fit is snug. The risk of this is that the contacts can bend in too far and break. Indeed that is the case with my 33C--the positive connector is gone, but enough of a stub is present to make adequate connection with the battery, but if I ever wish to resell the calculator purist collectors may object.
Due to the snug fit getting the pack out requires care--I just gently rap the calc on my palm so the end slips out a bit, then gently ease it out from there with thumb or finger. It is easier and safer to remove from the end away from the contacts, just as that end should be the last to go in when you put the pack in.
If you have the original metal sleeve from an original Spice pack, that is a bonus, since I am sure it makes a better and more reliable completion of the circuit than my tape and foil arrangement. Also, you can always just slip the cells out of the sleeve and charge them in a proper NiMH charger, since I suspect the Spice adapter probably takes a long time for a full charge. That said, after a few hours of charge in the calculator I fine that one of my makeshift NiMH packs will chug along for 18-24 hours at least in an endless loop program running at FIX 9. That is more than adequate for routine use.
The big objection to the use of standard size AAs in a Spice calculator is the potential breakage of the contacts due to a snug fit. I think if they are available it may actually be wiser to get NiMHs that have the recessed nipple at the positive poles. Indeed, if I can find such a beast I gather that is what I should use.
In the alternative, if you don't completely loathe NiCads, you can get one of waterhosko's Classic packs, disassemble it, and just use two of the cells. Indeed, I suspect if you are careful you can preserve the desired positive to negative connection between a pair and therefore not have to deal with a bit of foil or metal to complete the circuit.
Hope this helps.
Les