I use one of these adapters with a 675 hearing aid battery:
I believe there are similar adapters sold on ebay. This gives 1.35-1.4 volts and metering with my Himatic 7S is accurate. Just remove the battery and cover the + side with the tab provided or scotch tape and the battery will last (the batteries are inexpensive to begin with).
When metering in Auto lightly touch the shutter button and you'll see the needle fix in place - this provides an exposure lock of sorts, i.e., you can meter pointing at one thing and, holding the exposure, recompose on your subject.
Minolta cameras and lenses are excellent and reliable if you are lucky enough to come across one in good condition.