I have an off brand Chinese hot air/solder station (a Hakko knockoff from Circuit Specialists). While putting up a shelf, I broke the axle of the solder spool. Although I could have glued the center back together, one of the end caps just went missing so I made some measurements and just printed a new one.

Print all three pieces. If your bottom is "squishy" you may have to open the bottom part of the tube out with a hobby knife. If you get carried away (don't ask how I know) a little glue will save the day. But if your printer is lined up right the top part should just pressure fit with one of the caps.

The picture shows the red printed pieces and the black original pieces that were copied.