Alfredo,
I know this is a little late, but Grainger will have them, but they will be the type with a demountable hub. "Browning" is one brand I am familiar with. There are many others. Depending on the size of the pulley you need, I know you can get them and the hubs for 3/4" or 7/8" or up to 1 1/2" shafts (and bigger). The pulleys you may have been looking at are the cast ones with an integral hub. They come in both diecast and cast iron.
Aloha, Tony