I see people offering it on GTN, but none of them is willing to share where you actually get those recipes. So where can I learn the recipe for making Hilts/Mods/Enhancements or Armorings beyond 28 and what kind of recipes are there?
Generally, the way to get Artifact level blueprints is to craft and reverse-engineer the existing crafted items to get first blue, then purple recipes. Unfortunately, the doesn't seem to be green or blue blueprints for the mod items at Mark 30 or higher.
The only way I can see getting them is acquiring Underworld (rating 168) gear tokens, and then removing and Reverse Engineering the components you want from them (each RE has a 20% chance of granting the schematic). There's also the option of doing Level 55 HM Flashpoints, and spending the Elite Commendations you get there on similiar Verpine items with the modifications.
You can see a list of what items have an Advanced Might Hilt 31 here.