The origonal mercury cells are no longer manufactured, they were too toxic in land fill sites. There only are substitutes. Modifying the camera with a Shockey diode and using a silver oxide cell is simplest if you need to have it serviced anyway. Making an adopter from a similar sized battery for SR44 cells, the adopter has a Shockey diode, or using hearing aid 1.33v batteries, etc...
But with B&W or C41 film using a table is an ok fall back.
For the last 13 months I've only used a Kiev (or Contax), apart from folders, Fed's, Zorki's, M2, etc.,... and a digital to record dismantle sequences...