Over time I've picked up a few Harris jersey's, and other Mavs' signed hats, etc.
Last year, a friend of mine in Dallas offered to use one of their "2 signature passes" at the Mavs Meet and Greet during the pre-season to pick me up a new Mavs' jersey signed by the man himself for me! Cost me about $100 all up I think, was just totally awesome! Some of the other jersey's I have signed didnt REALLY come with "known" authentication, I mean I have the certs, but I don't 100% trust them - they were a nice price, so I bought them.
I also tried to acquire a pair of (apparently) game-worn shoes which were signed by Harris, but the seller wouldnt negotiate pricing and after stating they had video evidence from both the game, and signing they couldnt provide it to me upon request, so I let them go.