Oil pressure switch
Jason - Oil pressure switches are pretty much generic. Go to any auto parts store. Some have a stud like the one in the picture, and others have a male quick disconnect spade. Don't put tape on it when you install it as it has to make an electrical connection to the engine.
The thread is 1/8-27 (1/8" pipe). I made a pipe "T" so I could mount a second switch to run a buzzer. The stud is 10-32.
On the M-25XP it is on the starboard side below the manifold, recognizable by the single light blue wire coming off of it. The wire is probably painted the same as the engine.
If you can't get it off with a pair of pliers there is a socket wrench that is made for the purpose which just costs a few bucks.
That's probably more than you ever wanted to know about oil pressure switches.