Camper shell help?

Looking for a fiberglass (ARE, Leer, etc) for my 2015 longbed. I found one online for a decent price and went to pick it up but it was about an inch or 2 too long. Guy said it came off a 2021 I think.

Any tips or tricks to finding one appropriately sized for this bed? I didn't know the newer gen long beds were bigger.

Side note: Anybody happen to know where I can find one near Austin? TIA