Thread resurrection I know, but this is the post I found when starting out, but I eventually decided to go another route. Possibly less time consuming for those with a sewing machine and associated skills:
Use synthetic fleece. At least in my case it looks pretty similar and does not need to be hemmed.
Make a double-layered rectangle of the material that is bigger than your visor, and sew around the rectangle's perimeter. This is like a blank to keep the two layers together while you mark, sew, and cut in more detail. One long edge can be folded over instead of sewn. If there is a "nicer" side of the material that you want to be the exterior when you are done, that goes inside now.
Remove the visor from the car. Lay it down on the blank. Mark an outline of it, erring on the side of slightly larger, maybe a quarter of an inch. Since fleece stretches you don't need much seam allowance. Also mark where the clip-in rod point is, as you'll have to put a hole there so it can clip in.
Stitch around this marking, but start/stop such that there is a hole around where it attaches to the car large enough to slide the visor into.
Cut around your stitching.
Cut the hole for the clip-in point. If you are lazy (what I did) you can just do this to its exact side or even slightly smaller (since likely there will be some stretch as you put it on). If you want a more finished look (what would try to do if I were starting from scratch), cut a slightly smaller hole, then make some short relief cuts so you can fold it back in and hem it.
Optionally, but nice-to-have if the OEM foam padding is gone, cut and apply iron-on interfacing on the interior to give a more padded feel.
You may need to cut some fabric around the attachment-point hole, and may want to hem it afterward for appearance
Invert the cover so the stitching and the interfacing are on the inside.
Slide the visor into the cover.
Hand stitch the last part by the post that attaches it to the car
Here's mine. It's a bit rough: I cut too much by the attachment post, and if I were doing it again I'd try to hem around the clip-in rod. Maybe if I have time I'll do-over someday. This is not a collector car, though, just didn't want to be looking at bare MDF after the cloth disintegrated and ripped.