It sounds like he wants/needs to use his credit w/Ron Francis.
There are numerous adjustable switches in the $35-80 range. I don't know what the fan is, but my experience with the less expensive fans is that they don't last long. Using a switch that doesn't cut out until 170 is going to run the fan all the time and shorten the fan life, especially in summer NV weather. Using a switch that cuts out just above running temp would be a better choice in my opinion.
At least put a 3-way switch on it so it can run automatically, manually, or off when not needed.