jbracing,

I just went to Tower Hobbies parts store and found what you are looking for. There is no direct
link but go to Tower Hobies parts super store, then SuperTigre engines, then the GS-40, then
the carburetor assembly. Once you have the carburetor page open, in the upper right hand corner
there is something that says "Click for parts list for this item" Once you do that you will see all
of the parts for that carburetor including a "carb screw set".

It costs $1.39

Hope that helps,
Andy