Galati Gear lets you get a replacement strap for their discreet rifle cases. Expanding form 24" to 48" it can also work on any case that had a place for the end snap clips to attach.
Specifications and Features:
Galati Gear GLSP46MC
Single Padded Sling for Backpack Carry
Color: Multi Camo
Length: Can be extended from 24" to 48"
Fits: Galati Discreet Rifle Cases