Drill a 1/4in through-hole into the end of the gooseneck. The hardware is 1/4-20. Fits all cameras.
Use a piece of soft rubber as a cushion on the camera side.
The knobs I got from a dead radio.
Drill out the center of the knobs to a little under 1/4in. Drive the screw through the large knob to make usable threads. Drive the screw deep into the smaller knob, then cut off the screw head and clean up the threads with a file.
The smaller knob inserts the screw into the camera tripod hole, the larger knob is tightened to secure the camera. (Works just like them fancy store-bought thangs I betcha.)
The clamp works about anywhere. Tables, chairs, king-size waterbed headboards (use with discretion).
This project only took an hour to build. Bah!!!
Works great and is cheap and easy but would not qualify as a weekend project.