The leading goal scorer for the past two seasons at Moatside, is letting other clubs know he is in the marketplace.
Lock, 27, admitted this week he had not committed himself to Merstham for next season, but was "a bit gutted" so many players had left to join former boss Mick Sullivan at Leatherhead.
"I am sad to see them go, but it is true to say I do not yet know what I am going to do next season," said Lock.
"I have had a few chats with the manager Graeme [Banyard] and I am keeping my options open at this stage. I have been at Merstham three seasons and we have had a great run. New faces are going to be coming in as so many have left, and it has got me thinking about my future.
"I am ambitious. I want to push myself, but where that will be next season I am undecided at the moment."