Just found it on Amazon, I'm pretty sure it was this https://www.amazon.com/ARKSEN-Universal-Extension-Luggage-Carrier/dp/B07RM4HWMD
I have mine at the full 64", all I did was respray it with matte black Rust-Oleum and then apply a liberal dose of stickers. I do slightly regret not being a little neater about it but it's whatever
It came with the truck - Pretty sure it's this one (not sure of the exact size, haven't measured).
https://www.amazon.com/ARKSEN-Universal-Extension-Luggage-Carrier/dp/B07RM4HWMD
And it's at 153,000 miles