If you like the design of Prusa's T-bar spool holder but did not get one, you can print yourself a substitute. You won't get the same rigidity as the injection molded one but it should be functional.
The design prints in 4 parts that you can glue together.
There is a variant for the arms that has a higher torsional stiffness but may look less nice (always a matter of tastes there).
It's recommended to use full honeycomb infill for the arms and PLA is not a recommended material for this as it will slowly creep under load (mine is printed in ASA)
There is also a step file if you want to taylor or improve it