As the Sunlu Master is suffering of huge lack of design I've created this spool center to fit on my remix of the Hydra UnSpAd.
https://www.printables.com/model/548830-hydra-ams-unspad-y

I advise to print the sides slightly thicker (3.8mm instead of 3.4mm) to have a stiffer spool.

Also print the 70mm screw version.