The screw heads should be 11m/m or 7/16" - you can use either.
They're a funky shoulder screw, so don't lose them! I haven't gotten around to seeing if I can make more yet or not...
And, I really wish people would stop using WD-40 to clean contacts. I won't go into the whys and wherefores of it (again!) suffice it to say I've covered the matter in depth and in detail here before, as recently as earlier this month. WD-40 is not a "miracle in a spray can" or a "universal cleaner/lubricant," no matter what they try to make you think.
It can be used as a metal preservative (which is what it was designed for,) for removing sticky labels (it gets under the glue, but it's a bit difficult to scrub the WD off,) and as a lubricant for some machining operations (like turning aluminum,) but that's about it. It damn sure isn't a contact cleaner, and it isn't anything I want anywhere near any electrical contacts anyhow...