I use #675 hearing aid batteries, purchased in 8-packs in most pharmacies. They are
1.4v zinc air cells like the Wein cell, but the diameter is smaller. Three options for
centering them are: rubber o-ring, length of 16g wire (with insulation left on) bent into
a circle, metal skirt removed from hearing aid battery packaged as Wein cell. The
8-pack was approximately $5. They don't take up much room in a camera bag, and
while they don't last forever, I average 1 every 5 to 6 months. I use them in a
Canon FTb for the meter and am satisfied with the accuracy.