I like to use the brake light switch with the arm that is actuated by the pedal. not the plunger style but the swinging arm. One company makes one with an adjustable arm, it has a bolt thru the middle? I havent purchased one in 5 years and I cant remember who sells it? Its a company that makes other electric doohickies. thanks in advance.
I'm fairly sure this is the same brake switch Dr J is talking about. It's been cut down a touch. You may not need the adjustable arm depending on how you actuate it. The switches - to my knowledge - were designed for under dash use, but it works well on the 32. I've driven through some pretty deep water and it's never gotten wet far as I can tell. The pic shows one way to mount one. Actuating arm on the brake pedal is a 1/4-20 stainless allen that goes into a tapped hole on the brake pedal and has a lock nut to keep it in place.
Same style without the adjustable arm used on 1970 John Deere 110 Garden tractors for PTO safety. Parts still available , no idea of the price.