Unfortunately I've been through this unsuccessfully, even working with a local machinist. Les warned me it could be a disaster. The lower tube is threaded in the foot, with loctite, and a has setscrew with a point that rolls a couple threads on the tube. That is the tricky part. This damaged thread area has to be precisely machined out with an end mill through the small hole and cleaned with a pick. Then the tube must be held secure, heat, and with some luck its off. Any thread distortion combined with the loctite makes a mess of the foot threads and its impossible to remove after a few turns.
I've never seen a GG Zoke foot separately anyway so you shouldn't have to sweat this option anyway.
