Sid was a dealer in magical items.
Sid operated out of a back store in Gotham City, and had a wide assortment of ingredients for potions and spells. Zatanna needed chimera scale to locate Circe, which Sid would only sell for a price she deemed too high. Unfortunately, since Sid was his dimension's only supplier for the rare scales, Zatanna reluctantly agreed, but the spell failed. She was, however, able to get a refund.