So, let me be a fly in the ointment on the water proof (marine) grade switches. These are also used in Motorcycles.
I wonder if these are not such a great idea. While water is an issue, I believe that PT switch is marine grade (although it looks a bit bottom of the barrel, although my buddy who has a very nice case tractor has the same identical key). What I am driving at is that the issue with the key is not water but dirt. The more complex the tumbler, the more likely a jam. I would suggest that keeping with a simple switch, or going to what JJ did (more or less bypassing a key system altogether) would be the best solution. Marine grade is for water, not for dirt.
Carl