Shouldn't be that difficult to find, but they are in Australia!
Everything seems to be phillips head these days, or nothing smaller than 4 gauge, or not in oval head, or too long, or no shipping to OZ for small quantities - which ever it is, no one has exactly the right screws, and I only need 6 of them.
These are for screwing a plexiglas plate onto my Hammond organ.
Picture below shows what a slot oval head looks like:


