Corona 3 Typewriter Improved Replacement Spool Nut

The ribbon spools on a Corona 3 typewriter are somewhat unique. They will not operate without the spool nuts which both retain the spool, and select the direction of ribbon travel. Both spools are actively rotated clockwise during typing (including the spacebar), but because they are fed from the front (left spool) and rear (right spool), this clockwise rotation causes both spools to try to pull on the ribbon. Ribbon reversal is manual, you must loosen the nut on one spool, while the other one must be tight. Both loose, no movement. Both tight, something may break as they both try to wind.

These frequently are lost on these ~100 year old machines. You can't just replace them with a matching nut (if you can find one), as the originals are quite sophisticated, actually, they have a built-in retaining clip mechanism that uses a spring force to keep pressure on the threaded rod, keeping the vibration and rotation from unscrewing the loose nut (the one that is tight will be retained by t