Wouldn't recommend the Mercury cells. Might be a bit more "damaging" environmentally. Get the "675" 1.4V Zinc Air Oxide. Works perfectly for me.
I live in California where I can easily access a RadioShack. I think I just picked up a 6 piece roll dispenser sold as "1.4v 675 zinc air oxide" batteries for $7 USD. Loaded one up into my Konica, and whoo! It works!
SORRY! I meant 675, not 625. 625 is the battery that the canonet takes!