And there's the rattle can fusion paint that bonds to plastic. And pvc glue primer is a good surface prep, in clear or purple.

ABS dwv (drain waste vent) pipe is tough enough, and light enough gauge, to make a good snorkel, and comes in 90*, 45*, and 22.5* bends with slip ends. As does pvc electrical conduit, which is heavier wall than dwv pipe. I think you could run either unsupported from fender to windshield frame, which would let you do without brackets to the fender. You could make metal brackets that attach inside the door opening for the riser section. With dwv, you could use a rectangular floor drain fitting with a grate for the inlet. I would not glue the inlet, so I could turn it to the rear for heavy rain, unless I had some kind of float drain in the system somewhere.