This article describes an easy way to make a bolt holder from metal - in this case brass. If you want want your bolt holder to have smooth curves instead of tight bends, you can use a ball-peen or cross-peen hammer to forge it into shape. This has the added benefit of work hardening the metal, making it somewhat springier.
Process step by stepEdit
First cut a strip of metal from sheet and bore two holes near one end:
Next attach the metal strip to a vise so that the holes are clearly below the jaws:
Bent the strip to ~60 degree angle:
Make another bend a little farther to the opposite direction:
Next make two additional bends - first downwards, second upwards:
Now you can attach the bolt holder to the stock behind the nut with screws:
If necessary, adjust the bends angles as required.