Crossbars for Retrax Cover

Does anyone know where I can buy crossbar rails for my Retrax XR cover? Everywhere I look they are OOS.

 

Just so happens that I installed these today: Retrax XR bed cover (ordered over a month ago from a local dealer), Rhino Rack Vortex bars (from walmart.com), Yakima Skinny Warrior cargo basket (from fordpartsamerica.com), Yakima Locking Brackets (from quadratec.com).
The crossbars came as a package which included the crossbars, towers, track mounts, and two rails to mount onto a cap. You don't need the rails but I didn't mind paying a little extra for the package as I have plans for the rails and the package price was not much more than if you bought all the parts separately.
Here's the link to the crossbar package. It costs $418.50, no tax charged and free shipping. Mine arrived in 8 days.
https://www.walmart.com/ip/Rhino-Rack-Vortex-Black-2-Bar-59-Roof-Rack-Y02-490B-ST/133313919