"Some people are 'the glass is half full' types. Some people are 'the glass is half empty' types. I'm a 'the glass is full of radioactive waste and I just drank half of it' type. And I'm still thirsty." -- Bill Mattocks
The Leica CL takes a PX625 or PX13 Mercury Cell. The Wein Cell is Zinc/Air, and gives the same 1.35 Volts but lasts months after first used.
I have a reserve of Mercury Cells, fortunately they have a long shelf life. I am tempted to try some of the NiMH or NiCd batteries made for computer boards; some are small enough to fit into the PX13 compartment. The electronics companies sell them; Varta makes a lot of odd shaped batteries.