David, Are we talking about the one below the driver in the lower access? I got mine from Hector at CHF some years ago. I think it was less than $20. I could probably look up the receipt for it or you could just call his son. He tried to talk me out of by suggesting I jus tgo to a truck parts store and get one but I wanted his Eagle one.Have you tried Jefferson or Eagle?
On our MC-8 we installed a brake application pressure gauge. Normal braking is 10-20 PSI. A 60 PSI switch not not activate the brake lights except in a hard panic stop. We do have a 60 PSI N.C. switch for the LOW AIR warning. Our brake light switch is about 3-5 PSI N.O. (confirmed by watching brake application pressure gaue and brake light telltale). Hope this helps, Jack