Trader Zenkin:
Hello there! I knew you'd be coming. You are looking for Leorin's Mold, aren't you? It's true, he sold it to me once...but I'm a trader, not a warehouse keeper! I'm afraid I have already sold it to someone...
Well, I don't normally do this but...since you really need it, the person I sold it to is Magister Kaspar of Hardin's Academy. You can try asking him for it...he might be willing to exchange it with you for some favor. Good luck, then.