I just happen to be working on a couple of CLEAN OP41s. Rolex link screws have 3 measurements - length, diameter and tap (thread diameter).
It's useful to buy an assortment of link screws if you're going to be in the game awhile.
I measured the clasp screw in question as shown below. The closest match is an S14, with dimensions shown
It fits and the threads work. It's a tad long. You can live with it or sand down the slotted head.
I've sanded a good number of link screws, even the barrel diameter. The S14 screw barrel is a tiny bit too thick to fully seat in the thread recess so sanding that down may allow it to seat fully. You can put a link in a pin vise, clamp it to a bench and sand the barrel with a thin strip of sandpaper like a shoeshine cloth on a pair of shoes. Takes only a few minutes, just the thread end of the barrel needs a tiny bit of thinning.
It's a good idea to check link screw tightness periodically. Even better to remove them all, add blue loctite, and reseat them tightly. I don't do this enough, I had a rep fall off my wrist a few months ago while sitting at my computer. Luckily there's a small area rug below the chair - it was completely unharmed, whew.