Another is by a person in the UK. The web site is http://www.almostalien.com . The modular spindles there actually use a bobbin. Yeah! Unfortunately they are also expensive.
I like the bobbin idea because I could use my current lazy Kate to ply with.... As a type of test I might try getting a piece of rubber tubbing to use to hold a plastic bobbin in place on one of my current drop spindles to see if it will still work as a spindle with the bobbin on.
Here is my first try. This is using latex tubing It spins ok. I like it better on a spindle with a notch in the end
Here is another try using o rings. These are the very small ones. I find I like it best with two prints one on the top and one on the bottom. Then I use the one on the top and kind of push the bobbin over it. This will help to make it so the bobbin does not rotate.
The o rings are easier to get on and off the spindle when compared to the latex tubing