I make them out of hyd tube; bend them a little, flare the end, and I braze on a washer for the boot stop. Pretty easy process.
At one time, either Cling's or Snyder's made and sold them.
I've done it, just used a flairing tool for tubing to make a flair on the end to hold the rubber dust boot in place. I think the tube size is bigger than common lines at the parts store, but I had an old chunk of hydraulic line that was perfect.
I make them out of hyd tube; bend them a little, flare the end, and I braze on a washer for the boot stop. Pretty easy process.
At one time, either Cling's or Snyder's made and sold them.
I believe they are reproduced.
Boling Bros. sells those tubes. look here:
https://www.bolingbrothers.com/replacement-parts/
You can get the exact tube size through McMaster-Carr. I did so many of these I had purchased a 3' piece.