Of course Disney being the merchandise marketing machines they are couldn't resist putting all the artwork on a range of merchandise. You can check out and see all the merchandise that was available for the event here.
Unfortunately, the majority of the merchandise that was available for the event has sky rocketed,but check out Ebay and you might find a great deal.
There was a Mickey Mouse Haunted Mansion SHAG hat.
Hurry back, hurry back........don't forget to bring your DEATH certificate!!
(P.S. I'm making it my priority to be there for the Haunted Mansion' 50th birthday.)