Khiro offer a selection of flathead skateboard hardware in a selection of sizes from 7/8" in length up to 3", which are suitable for use with a phillips head screwdriver.
Each pack contains 8 flathead bolts and axle nuts, but there are bigger, bulk packs available which are suitable for retailers.
With Khiro's wide selection of hardware you're bound to find what you're looking for.
Prices start from £3.49 - £25.95