Hi - I have an '83 Burro
, it had a rockguard on it - basically it's a curved aluminum frame holding a piece of opaque plastic or fiberglass; I mounted a 36" stick of 1"x1" tube aluminum by through-bolting to the front, above the window, using 3/8" stainless steel bolts,with a 1 1/2" x 12" piece of 3/16" aluminum as a backing plate.
then I used a plated piano hinge to connect the frame to the tube aluminum, and attached the support arm (you can use those struts like on a hatchback) by slicing 1" x 1" angle aluminum, and through-bolting them in place right through the window frame.
Since I started with something, I could adapt fairly easily...starting from scratch means you's need to be more creative. Scamp
, I believe, sells a shield that clips on - check their website.
Either way, I agree with you that water will find a way in through the window panes if it isn't diverted by some type of guard. Plus, it keeps bugs off the window!