Might even just need to modify the current slide, get like a smaller tube to put through it? Dunno. not too much of a fabricator..
Worth mentioning also, ever see the dual visors on some Fords?
I know I've seen it in Expeditions but those are huge. My aunt has told me about them in her old Explorer. My old 94 Taurus SHO had manageable sized ones
Here's an Expedition's
Basically you get one to cover your side and the front AT THE SAME TIME