Yeah, the Broken Shieldblade can be repaired through a questline started at the Creon Embassy. In order to start the quest, you need to have completed the vanilla Glitch mission, and have the Broken Shieldblade in your inventory. Head over to the teleporter area of the Creon Embassy, and there should be a female NPC hanging around near that area. The NPC can wander about a bit, and can accidentally hitch a ride on the elevator if you use the elevator.

The quest you get from that NPC is named "Excalibur Reborn". It's got four quest steps, and you get the repaired weapon at the end.

The ID for the repaired weapon is "thea-excalibur".

Thank you very much! I had a feeling this morning that it had to have some connection with the original Starbound quest.