After a very lengthy search I have finally found a source for both 18 and 20mm black button head stainless steel M3 screws. I also managed to get a hold of black M3 stainless nylon lock nuts as well, making the tricopter look very pimp.
The screws are much stronger than the old philips screws. They have a temper rating of 10.9 and have 2mm hex heads that are very low profile. Only downside is that they are more expensive than the old screws so I had to bump up the price of the individual screw packs a bit. The Tricopter kit price however stays the same.
Since the screws showed up one day early the back ordered tricopters will start shipping out tomorrow instead of monday!