Personally, I always think custom screw drivers are the way to go for any precision work. Got in the habit of this when I was working with old or accurate replica rifles which either had hand cut screw slots or some very odd size no longer commonly made. For tip screws, I just get the smallest screwdrivers with a nice solid handle at the hardware store. about $2 each. (I hate the twizzling ones in sets, and they usually have crappy steel for the blades) About 2 minutes work with a fine file produces a very precise fit for whatever screws I'm working with.