Is there a replacement for the Mallory RM450 battery?
Yes, but not exactly. The Mallory RM450 was a 1.35V mercury cell battery used in P1, P2 and P3 cameras. It measured 11.6 mm in diameter and 14.5 mm in height; unfortunately, there seems to be no modern replacement of that exact size. The good news is that batteries of the same voltage and diameter exist (Zinc Air Cell Z675PX or the Wein Cell MRB675). However, both only have a height of 5.4mm and some sort of conductor is required for the battery to make contact. There are adapters available on eBay and elsewhere that make up the height difference. Some users even suggest using tinfoil, stacks of metal washers or springs as a conductor.
