Find the core weapons file in the >stardock>elemental install location, use search if you can't find it. Copy it just in case you mess up anything. Every item is listed here, find the one you want to be avilable and remove string:
and replace with
The number in the middle being the cost of customisation points, this can be set to 0 for free gear.
Copy the weapon files and create custom ones in your my documents folder and do the same method above, you can now edit other values etc without touching your core file. (This is the method i use)