I can assure you that I started my 6 LC 475 yesterday to (check their hard drives), without batteries using the PRAM keystroke.

When I need battery I just sold two standard "AAA" batteries together, then to the motherboard. It's not pretty to look at but it works.

I do that only for the machines that I really use, otherwise I fear theses batteries would spill and destroy the motherboard when getting old.