Be aware there are 2 thread sizes for 1/4" screws. The ones you want have 20 threads per inch and are referred to as UNC (unified coarse) as supposed to UNF (unified fine) which have 28 threads per inch.
Here's some suitable stainless steel screws in assorted lengths: 1/4-20 Hex Head Machine Screws
Good info but if the home made feet are going to be anything similar to the SVS feet, hex head are no good. They need to be pan head type bolts in order to be able to be fixed with a Philips screwdriver or Allen key.