I have a Retrax Pro XR for Ram 1500 5.7, it was purchased new in December 2020 for my 2021 Ram. My truck is a lemon buyback for unsolved electrical issues, so i have the the accessories that i am taking off of the truck.
EDIT: this fits a standard type bed, not a rambox - i just noticed the OP's spec.
It's in excellent condition, maybe some minor scuffs from being used for barely a year. It has the T-slot accessory rails and is very dirty in the photos from parking under a messy jacaranda tree at work.
I'm located in Los Angeles, DM me if interested.