www.jgbraun.com has them in 5 different materials (aluminum,pink bronze alloy,steel,304 stainless steel and brass),and in sizes from 1" to 12" diameter. Price for 1-1.5" (steel) ball is $5.56,1-1.5" (pink bronze) is $11.80.
Pretty cheap for a weapon.I just bought 8 1.5" in ‘pink bronze’ and 2-2" in 304 stainless.
www.salemball.com <—even better.
Surely you can find a place that sells ball-bearings (which is all they are) for a cheaper price than that, can’t you?
(And I know it’s not fair to you, but everytime I think about this I laugh at the “Batman” slam somebody wrote about you…! Sorry…)
K. Mark Hoover
I actually had a hard time finding a company that sold the larger bearings,most of them sold smaller ones (.625" and smaller).Yeah the ‘batman slam’ was kinda funny,but it will never be as popular as the JWT belt-buckle. 
I missed the Batman slam, what was it about?
Adventure is just a romantic name for trouble. It sounds swell when you write about it, but it’s hell when you meet it face to face in a dark and lonely place.
Louis L’Amour
Weapon-maker was going on how he used ball-bearings as a handy throwing weapon–feeding them from a pouch at his side.
Somebody questioned the effectiveness of such a “utility belt” and called him “Batman.” They also said they were interested in much the same thing–when they were like, seven.
K. Mark Hoover