When I finally got the clean out screw out(with an impact driver) I took it to my Ace hardware, found a metric nut that fit, then got screw (not a cap screw but similar, forget what it was called) that fit.
It takes a 3mm allen wrench, which I like much better than the straight slotted screw.
The shortest they had was about twice too long, so I bought a couple nuts, put them on the screw,
and cut to length with my Dremel. Rounded end slightly, removed the nuts and it works great.
Screw comes with a domed head and a flat black oxide finish, so it doesn't stick out like the proverbial sore thumb.