Never seen a ready made CAG in frame mount, thats something you would have to fab. up yourself, and would only be the begginning of all the fabricating you will be doing inorder to get a cag mounted in frame and working nicely on a bicycle, it can be done of coarse, but will require a good amount of building to get there.
Not sure why you would be looking to go with a cag engine inframe but I would lean towards just putting a china girl 66cc engine in there and building around that, much easier unless you have all the tools and fabricating skills needed to go with a cag.
best wishes on what ever you do.....
Peace, map