Hamish,
Re:Minox 35 EL, When the original 5.6v PX 27 became obsolete I bought one of the adapters which allows the use Two lithium 3v CR1/3N batteries, Okay 6v but these are far superior to the original and can be purchased as single CR1's or a PX28 and split.
Whitby swing bridge (before the malfunction)