Attaching metal pipe to wood - what type of fittings are these?

[Josh Davidson]

I'm attaching a few pictures of a shoe rack that we're currently using. I'd like to build something very similar to this, but make it a bit taller and replace the telescoping rods with straight pipe. I'd like to use the same style of fittings that the current piece uses. I'm attaching a couple pictures that illustrates what they look like. Essentially there's a male stud that screws into the side of the shoe rack and there is a piece of rubber/nylon inside the pipe that creates a tension fit when slid over the stud.

I've been searching all over trying to find similar fittings. I can't reuse the existing fittings because I need 4 more and the current pipe is 1/2" ID, which I can't seem to find anywhere as well (just 1/2" OD). Anyone know where I can find similar fittings and finished pipe to match?

Shoe Rack: https://imgur.com/Kg7HHN8
Fitting System: https://imgur.com/b4oCQTc
Stud Fitting: https://imgur.com/O40MiBB

[Jamie Buxton]

The fitting would be easy to fake. Get a wooden dowel whose OD is close to the ID of your pipe. Cut off a section which is a half inch long or so. Drill a clearance hole along the axis. Screw it to your cabinet sides.