Quality 7 purple weapons have one skin each; same one as skin #1 for Quality 9 Blues.
Availability: Crafting or very rarely as drops. It would probably be easiest to craft Quality 9 Blue weapons to get the skin you are after.
Quality 7 weapons have two skin each.
Availability: Crafting or drops.
Quality 7 weapons have three potential skins. Which skin you get while crafting is random. You usually can’t tell by the item icon in the crafting panel which skin it will be.
Availability: Crafting and drops. (Mission details to come.)