I tried two replacement pressure switches from junked bikes at the local junk yard for my CB550 and both of them quit after a short time. One of them went dim and would not light the indicator enough, and the other stuck ON and would not shut off. I searched for a new one locally that I would not need to order, and found that some years of the Honda Prelude used the same one. Well when I went to get one they were discontinued. There is a replacement part however that does work, with a little modification. The new part is;
Niehoff Oil Pressure Switch, Part Number: OP23741.
http://www.partsamerica.com/ProductDetail.aspx?MfrCode=NIE&MfrPartNumber=OP23741&PartType=417&PTSet=AHere is the picture;
It is a bit taller that the original switch so it wont fit under the side cover without trimming the threaded wiring connector. To get it to fit I took both nuts and washers off the tip and then reinstalled one nut as a spacer. I then got out my dremel with a cutoff wheel and cut the connector thread off flush with the nut. Next I installed the Pressure Switch onto the Oil Pump. I then used one of the washers underneath the wire eye lug and tightened it down with one of the nuts. It now has enough clearance under the cover to work. And it is a brand new pressure switch that works great, and only costs $9. Enjoy.