I would go to Michaels, and look at the packages of craft and sewing pins. They have
them in many diameter shanks with decent smooth heads on them. You can get them in
a semi-blackened dark gray or black too.
The screw has probably enlarged that hole (as has already been pointed out to you). But if need be,
you can fill it with some JB Weld 2-part epoxy (find it at any auto parts store or auto parts department
in a department store). Then use a pin vise to drill a new smaller hole.
The pins on that engine were plastic so they "crush" a little in the holes and stay put.
Be very careful with them.
The Hob Bits hex head screws should work well, but the heads will be thick. (Not "wide", I mean "thick")
They will stick out far. But you can fix that by carefully filing down the face of the hex head. If you paint them
silver, they should look really good.