All the plugs from 94.5-03 were the same size.
If the plug you tried was to small then someone tapped it bigger

 

you may be 100% correct fp but I'm hoping that since his has the 1/4" square drive that mine had it might actually be the same. I'm wondering if this isn't an aftermarket reservoir but I doubt it.

 

The 94.5 and 95's have a different front engine cover and the reservoir cover is also different from the 96-03's. Both the Oil Pressure sensor and fill plugs are regular pipe thread fittings. You should be able to pick up a brass plug from the hardware store, I just don't remember what the NPT size is.... too many years ago.