IP67-spec throttles?

Question - Most of the electric throttle solutions I've seen are pretty cheaply made, and if left in heavy rain will likely saturate. Does anyone make a fully waterproof sealed throttle assembly?

Generally, a hall sensor is going to be safer in the rain than a potentiometer throttle. One option you have is to disassemble a hall throttle and seal off the wired bits with some silicone.

Another option is to make a 3-button throttle as I had designed in my build thread, and use IP67 rated buttons.

Or use a cable-operated throttle (like a motorcycle or scooter or ATV, etc) and put the throttle inside a waterproof box, either as a whole throttle or as just a hall and magnet in a box (or a potentiometer as a potbox).

The Domino throttle is reportedly IP67 rated. The rating has more to do with the design of the mechanism than with whether the device is a potentiometer or a hall sensor. The pot tends to be very linear and have a wider range of output voltage, whereas magnetic devices vary considerably in their linearity (many are very poor).