I printed 2x https://www.printables.com/model/92530-peter-quill-star-lords-quad-blaster-guardians-of-t and then had my hands full. I searched around and found some designs for holsters, but not for this blaster. I modeled one from scratch using OpenSCAD, based on existing designs. 

Print one of each Right and Left. 

Use black zip ties to create belt loops.