Carrier Command 2/rom_0/scripts/screen_inventory.lua
Then search for the following text, line 808 at time of writing:
table.insert(items_locked, item)
Change to:
table.insert(items_unlocked, item)
Otherwise, I have added a pre-made file with the changes on it if people want to download it and replace the screen_inventory.lua file.
Note for multiplayer use:
Please make sure everyone you are playing with is fine with you using the mod before using it, as it will still be active when you join multiplayer with people not using it.