Yakima HitchLock for Yakima Hitch Mounted Bike Racks - Same Key System (SKS) Yakima Trailer Hitch Lock Y07235
PACLOCK's TL80A-YK-1 Hitch Lock, Buy American Act Compliant, Compatible with Yakima Bike Racks, Blue Anod. Alum, High Security 6-Pin Cylinder, One Lock Keyed to #26544 w/ 2 Keys - Amazon.com
Advantage SportsRack Threaded Hitch Lock 5/8" Diameter Pin in the Trailer Hitch Receivers department at Lowes.com