Solder one end of a piece of brass tube and put it in as a plug. You can just fill the end of the tube, or pinch it before soldering. Or maybe use an old drill bit, or even a piece of wire such as a remnant from a small landing gear. The problem with a screw is that fuel will travel along the screw thread. If you use a screw, use a long one with a smooth shoulder where it's not threaded.
There are lots of options.

Tim