This is an easy source for 18-8 stainless ones. Futures use 1/2 length and fcs use 5/16 length.
Both use 10-24 threads.
NASXXXXXX where the X's are numbers that designate a specific thread size, bolt style, and bolt length. They're much nicer fasteners and will be harder to strip. Unfortunately looks like they only come in fine threads so can only find 10-32 and not 10-24.
The link above should be easy enough to order through and is a lot cheaper than buying branded fin screws. Just take a current screw you have to a hardware store and confirm a 10-24 but screws onto it before you order.