Try this company, I use them to source replacements for mercury batteries myself.
The website might be old hat etc but the company provide a really good service with my previous set of silver oxides turning up the next day.
I also just ordered some for the Minox today as well.
Oh and silver oxides is the way to go, alkaline and lithium just don't cut the mustard.
http://www.smallbattery.company.org.uk/
I use this guy for battery adapters all my old cameras that require mercury batteries,
http://www.paulbg.com/Nikon_F_meter_batteries.htm
Extremely helpful, quick delivery and very good value