Hey, tu can correo electrónico his agent on www.knightkids.co.uk
o tu can attend a sci-fi convention that he's at, however tu could be charged for an autograph. tu can keep up to fecha with sci fi conventions with Gallfrey Base, sarah-jane.tv o sarah jane adventures news (cough cough) :P
Okay, I'm not too sure about this, follow this link link and find his agent's address and send her/him a piece of paper with a blank el espacio at the bottom asking him/her to send it to Tom and put escritura to him to sign down the bottom but be polite.
If tu buy one tu can request a certificate of authenticity to prove its real, i bought some, they are the people who sets up the sci-fi conventions he goes too, then must have got Tommy to sign several autographs