There are "roofing" types of bolts m3 about 6mm or 8mm that will suffice as well, large flanged heads but flat head screwdriver. You need bolts not self tapping screws. M3 bolts
I use those screws myself they are perfect and hold nicely. A lot of the bolts are Allen key heads from what I found and it's much easier having a Phillips head to screw in than messing with an Allen key.
