Rail buttons or guides for model and high power rockets launching from 1010 or 1515 size slot aluminum extrusions. ( https://www.8020.net/ ). These are not as strong as the delrin or nylon versions but hey you can easily make this yourself. The 1515 guides are set to use 8-32 screws but could be opened up a bit for 10-32 screws with a 3/16" drill bit.
Use support so the upper disk of the button is supported and straight. This is the portion that is inserted inside the rail and most critical for fit. Alternatively you could print these upside down and have the inside rail portion cleanly built. Your choice.
I used three walls (1.2mm) .
Clean the support material out with your favorite finishing tools.