Perhaps see if anyone has a replacement link. The screw to match the replacement link should come with it.
Then remove the link thats missing the screw entirely.
I find a lot of the links themselves are (visually) interchangable.
Lately when buying a M2M Rolex rep, I've been harvesting links from one to make the other larger... and you'd never know to look at it.
Its super hard to get the screws from one link to fit the other though. I have a little styrofoam egg crate on my bench I use to make sure they don't get mixed up.
You'd think it might occur to someone to standardize stuff like screws and links then make a bunch of them that would be a fit for each new generation of SEL and case. You'd think that'd make tooling, etc easier, boosting efficiencies and lowering costs. But nah. Must be a good reason why not, but I have no idea what it is. LOL