Here's the idea:
You purchase a Scroll of Purchasing (or whatever...)
Inscribe it with what you're looking for and however much you're willing to pay. You drop it in your house along with some money.
Players can see your "purchase orders" and fill them for you if they have the appropriate item...
Selling to player shops
Re: Selling to player shops
... or a simple bulletin board where you can put comments like in TomeNET.