I've successfully used a zinc-air 675 hearing aid battery with a #9 O-ring in a number of cameras, but not sure if that will work in the Rollei as it requires that contact with the battery be at the top and the bottom. Jon Goodman (of camera foam fame) sells a machined adapter (http://rick_oleson.tripod.com/index-149.html; about 2/3s down the page) that should mitigate that issue.

However, the zinc-air battery requires air to activate. As I remember, there is a screw on cap to the battery compartment. If it's air tight, you may need to drill a small hole in that cap.