Can you draw a picture for me:yes: I think I know what you are talking about but really suck at visualizingI think you can make one. If you are only looking to push the fence, then consider a connector nut used to join two sections of threaded rod together. About 1in long, easy to clamp under the "C" clamp and save the time of drill and tapping.
If you make a U shaped box for behind the fence, you can have the threaded rod go through the bottom of the "U" and then drill a small hole for a cotter pin with washer behind. Lock nut on the other side and now you have a design which can pull as well as push. If you are not picturing this, it is the same idea as how the handles attach to a Black and Decker Workmate.