Also I just realized that I don't exactly understand what you're trying to accomplish. As far as I understand, finding a gooseneck mount with the hole (but no clamp) is quite easy - it is the clamp itself that is rarer.
Are the mounts with the clamp particularly hard to find nowadays? I have two mounts (one with no hole/clamp and one with the home/clamp) and I did not pay much for either unit.
If you really want the gooseneck mount with the clamp, you should probably be able to hunt for an original unit.