The product we used on this project was crushed oyster shells and I believe it is the best, most consistent product for bocce. We have used "breeze" before, which is a basically flagstone crusher fines. Breeze is very similar to what is used as an infield mix for baseball fields. I am not sure what part of the country you are in, but 1/4" and smaller crushed stone would probably be a decent substitution, as long as it had some fines to help lock it in.