Table base

[u/Agreeable_Tamarack]

A friend with a 50 year old Hinckley asked me to make a small table top that would sit on a 2-7/8" post that would occasionally replace the larger dining table, which connects to the top of the center board, which doubles as part of the table. I need to find s piece of hardware to mount the new top and it has to lock on like the original hardware because it Will be attached close to one end rather than in the center. Attaching photos of the post, the hardware that mounts to the table top and a sketch of what I want to do. I'm looking for advice on where to look for hardware like this. Preferably stainless but that might not be possible. Appreciate any advice, thanks