This is a fully customizable parameterized model in Fusion 360. I have included 4 different variants in this thing, but you can easily make whatever size you need by editing parameters in the Fusion 360 file.
4 parameters adjust the size and shape of the g-clamp, as illustrated in the line drawing. The length of the screw changes automatically when you change the clamp size.
After making your changes you can right click on the "Printable Orientation" component, and select "Save as STL" in the pop-up change the "structure" to "One file per body".
(If you want to make it very large or small, consider using the parameters to give it the proportions you want, and then scale the whole model to the desired size in Fusion, or in your slicer. That way, the size of the screw and the button will change with the size of the clamp.)
There is a stress analysis already set up in the Fusion 360 file, so you can see what effect your changes have on the strength. (There seems to be a bug in the way Fusion 360 handles the archive file. So if you want to run the stress simulation, you will need to go to "Simplify" and remove the "Printable Orientation" component from the simulation, before you run it.)
The model prints without supports, there are 45 degree overhangs and a very short bridge section inside the threaded hole. I recommend printing it with at least 3 outer perimeters and 25% or more infill.
This is a simplified version of my g-clamp with quick adjustment mechanism, which is here:
I've never charged anything for any of my models and I don't expect tips, but please post your makes, it makes it worthwhile for me.