The meter is working now.

I just opened the bottom end of the camera and super-glued the negative contact back onto the plastic part of the battery holder and it now conducts.

I also obtained an adapter that allows me to use 357 type batteries and the meter is working fine.

Looks like I am going to have to replace all the foam light seals as well.

It might not need insulating from the body case because it looks like there is a small amount of non-conductive paint at that area, but should I consider putting some kind of insulating material between the case and the negative battery terminal?

I am also trying to figure out where the battery door leaf spring goes.

I can't find a blow-up schematic of the this particular camera, but I did find one of the G-III 17 which shows almost the same leaf spring and it is placed pressing at the hinge of the battery door on within the lower or bottom camera plate.

Does the battery door leaf spring in the Canonet 28 fit in against the hinge in the same manner?