Loot kits are special devices you can get from Junk Dealers in major cities. The Junk Dealers who give loot kits will always have all 5 types available, but note that you can only have one loot kit assembly device at a time in your inventory. If you are stuck on some kits, you can store them in either your deposit box on a Bank Terminal or your house and the Junk Dealers will allow you to take another one. Note, you may need to have an item salable to the junk dealer in the top level of your inventory to access the conversation chain to obtain the kit.