The 69-year-old from Devizes, Wiltshire, has not been seen since 25 September.
Extensive searches have been made since then involving helicopters, mountain rescue teams and search dogs.
At the weekend, more than 50 mountain rescue personnel were involved in searches of Glen Coe.
Mr Garton is described as 6ft 2in tall, of slim to medium build, with fair, thinning hair. He occasionally wears glasses.
Police divers made a search of the River Coe in Glen Coe on Tuesday in the latest effort to find missing hillwalker Robin Garton.