Quality 8 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.
Note: After making 104 chaos focus weapons, I had still not gotten the Chaos Focus 3 skin. It could just be horrible luck on my end but at this point my recommendation would be that if you are after the Chaos skin #3, it’s better to buy it on the auction house rather than trying to craft it.