Some years ago I bought a small set of parallels, sold as follows :

• 4 Pair 5/32" x 3" Precision Parallel Set 
• 1/2" - 7/8" Machinist Toolmaker 8 PC
• (2) 1/2 Inch; (2) 5/8 Inch; (2) 3/4 Inch; (2) 7/8 Inch

.They came without any kind of holder, so at the time I made a makeshift holder out of wood. I finally got around to making a better holder for them. 

Looking online, I see that these same parallel sets are still being sold. You can get them without a holder, or for twice the same price you can get them with a holder! Or you can just print this holder for about a $1.

Print Instructions

Print in PLA using the 3mf or gcode files provided.

Note that the size designations you can see in the photo are recessed numbers in the print. I highlighted these numbers using some diluted acrylic paint.

CAD

The OnShape 3D CAD files for this are here :

https://cad.onshape.com/documents/6c40e754fc1712dad6aaf28e/w/6cf0ad3812ee5fd9693b950a/e/ce7b9f77a895811a45c1b1a3