You could always use a jock-strap, but a strap specifically designed for packing works so much better and keeps everything in place. Trans-owned Aslan Leather makes this awesome packing strap with an elastic strap and leather backing to hold your favourite packer. Originally designed for the Vixen Creations Mister Right, the Aslan Leather Packing Strap works great with New York Toy Collective Packers, Doc J Packers, and the XS, Small, and Medium packers from Fleshlight.
Sizing:
XS: 26" - 30"
Small: 30"- 34"
Medium: 34"- 38"
Large: 38"- 42"
XL: 42" - 46"
XXL: 46" - 50"