[Mr P]

A curious booster could be one called "Munchkin Characters" or "Money Bussines" and it should be based in those characters (actually NPCs) that you can found in any RPG game. They always offered themselves to help... by the right amount of gold. You could use theirs skill just once time, like a one-use item.
I.E. :
Garb Eachman
Garb will sell you any object in the dicard pile for the price of it... and 100 GP more.
T.H. Ief
Mr Ief will steal any small object that has a player in the table for half the cost of GP.