Have placed many siding orders with All-Rite.
I think they have two locations, CA & GA(?).
https://www.all-rite.com/aluminum-siding-metal.html
I send them a small sample of my siding and they custom make it.
https://www.rvpartsnation.com/rv-exterior/rv-siding/
Also check with a local sheet metal shop.
Bring a piece of the siding for them to give you an accurate quote.
I've done dozens of siding jobs, the local RV suppliers/shops in my area were useless when trying to get stuff like this.
I guess they look at it like if they sell the siding they are losing a siding job for their shop.