You pretty much need to find a used pulley, or a new one from the Honda dealership. Not much chance of getting an aftermarket pulley as they arent typically a wear item.
Its not too hard to change. I think its a 17mm nut with a lock washer. Just put a screwdriver through one of the holes in the pulley to lock it while you turn the nut, and the pulley should just pull off. You may need to tap it a bit with a hammer. There is a key on the pump shaft that may fall off, make sure you dont lose it, assemble in reverse order, and your good to go.