I installed a grab "strap".
Take the visor off. There is a hole there. Stick something in that hole, and probe down toward the door. You'll find a space in there.
Drill through in the best spot. Drop a 1/4-20 bolt down through your hole. Put a washer on that bolt, first.
Fold a piece of nylon strap in half. (I used a piece of a rather large ratchet strap.) Burn a hole through the folded over strap, using a hot bolt or nail.
Slip that strap over the bolt that is now hanging from your roof. Add a washer. Then a nylock nut.
Reach into the first mentioned hole, with a bent wrench, to hold the head of that bolt and tighten the nylock nut down.
Now replace your visor.
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