If you mean the ones on the curved tinted plastic rock guards, I believe they are called Dzus fasteners.
Here is one source .........
They are used in many applications - aircraft, old sports cars etc etc
I have them on a two piece aluminum protector that protects the sump / oil filter / rad overflow tank under my Honda Goldwing bike.
But no doubt they have many sizes so you might be best to order direct from Airstream to ensure proper fit. Maybe try calling Jackson centre although they may tell you that youwill have to order through your local AS dealer.