Have ordered from All-Rite many times.
I send them a small sample of the siding I need along with lengths and quantity I need. Has always been a virtual perfect match.
If you can keep the lengths 8' and under the shipping won't kill you.
I have successfully made some discrete length-wise splices using white rivets to pull of some really long runs with 8' pieces.
Once all the doors, hatches, windows, trim & decals are on the splice gets lost in the mix and almost looks factory.
https://www.all-rite.com/catalog-mai...-aluminum.html
https://www.rvpartsnation.com/exteri...r-rv-aluminum/
https://www.lonepine-rv.ca/siding/