U can have him sign a peice of paper, make into a decal/sticker and u can stick it anywhere in the car and if it gets messed up u can make another. If none of these ideas appeal to u hope u find a solution.
P.S.- if u do get it signed on the paper jam send it to me on an e-mail so that i can print it out as a decal for myself if thats at all possible. Thanxs bro.