"No one has had any contact with Simon for a long time now and that is causing us concern. He gets out and around the place on a regular basis but he has not had any access to his bank accounts, which is unusual, so that is why it is of concern," Mr Friend said.
"He is well known, he hitch-hikes around quite a bit."
Mr Fuller is described as having shoulder-length brown hair, a full-length beard and is about 177cm tall and thin.
Mr Friend said Mr Fuller's disappearance was "not suspicious at this stage".
"I wouldn't suggest that there is any connection to hitch-hiking and us not knowing where he is, he could have just gone somewhere that we are not aware of."
He asked people to continue coming forward with any information on Mr Fuller's whereabouts.
Anyone with information is asked to call the Hamilton police on (07) 858-6200 or CrimeStoppers anonymously on 0800-555-111