If you wanted to stay with Nikon, you could take a look at the FE/FM series. They are smaller bodies that are mostly manual, although certain models offer autoexposure.
If you do move to Olympus, you'll be buying into a system that is highly regarded by its users. The bodies are well made, and the OM-2 uses S76/LR44 batteries.
All Japanese cameras from the 1980s and earlier will need new foam seals, which are simple to replace.
The Olympus was a full-system camera with a huge selection of lenses, winders, motor drives, dedicated flash units and more. The OM-2 also has a sophisticated metering system. You will need to get used to having the shutters-speed dial at the base of the lens, but if you shoot mostly in automatic, it's not a big issue.
It's aperture-priority, so you'll want to keep an eye on your shutter speeds as you shoot.