My old spec says to use Silica sand, but I see that you do not offer sand anymore.
Your old spec calling for silica sand is outdated. Silica sand should never be used for blasting. Please see our website here to learn the hazards of blasting with silica sand.
The reason your spec calls for silica sand is because it is virtually free of iron oxide (Fe2O3). All abrasive will leave a small amount of material on the surface after blasting. Iron Oxide is dissimilar to stainless steel and can cause a galvanic corrosion on the surface. Blast materials that are free of iron oxide include walnut shell, glass bead, crushed glass and aluminum oxide.
I have had many customers use fine Green Diamond, Starblast and garnet with success to help reduce cost. If you must use an iron-free product and you have a large area to blast, the most common answer is to blast with an inexpensive abrasive first, then sweep blast with aluminum oxide or glass beads as the last abrasive used per spec.