My Nikko Stirling Targetmaster's zoom is a bit difficult to turn and grip is not great.
So looked at few options.
There were a few good 3d printed designs but being in Piketberg this was not easy to access.
Got a design plan online:
Went to local Argimark and found a part that could fit. The Nikko targetmaster has 43mm radius at the zoom.
Wanted something plastic - easy to work with ( only basic tools available )
Next was cutting the plastic to help fit better ( at the area where ring is pulled together )
Used candle to heat a scalpel and cut the plastic.
Got thin 2mm piece of rubber to put on inside (protect the scope) and glued this to the clamp with contact adhesive.
The screw and nut was cut to size and placed into position and secured.
Now there is more leverage and grip to turn.
The design should fit most scopes with some modification.