If you want to save some money and electrically inclined, I squirreled away the sensor number that can be used to put the kit together yourself. Buy the switch of your choice and a fuse holder (if you don’t already have them) . You could get the 1/8” NPT 90-degree fitting and some wiring (if you don’t already have it) at your local hardware store. You could use the Monster video and the diagram on their site for the wiring. It takes less than $30 worth of parts to do it yourself.
Normally Open Oil Pressure Switch - $12 at Napa (don't know the cross-reference for other brands)https://www.napaonline.com/p/ECHOP6624
Eaton Fitting - $2.14 at Amazon (should be about that at the local hardware store)https://www.amazon.com/Eaton-Weatherhead-Fitting-90-Degree-Female/dp/B00USZZ3LS
4 Pin Weather Pack Connector - $6 from eBay (it has the female ends and the pins (some sell the connector without the pins)
Switch of your choice – starting at $2 from Summit