If you want those bolts to be exactly correct then remember that a major problem for many steel suppliers will be the hexagon sizes. Cycle threads use the same hex sizes as BSW/BSF bolts and these are specific to the bolts and not standard AF sizes.

I tend to make these in stainless because, strangely, the hexagon sizes are available if you know where to look. I keep a small stock, and use a supplier if I need larger quantities.