These items are available as parts of kits. All are included in at least one pre-made kit, so you can try them out. They can also be obtained as part of a custom class. There is no way to create more in-game. This suggests that the art of making these is now forgotten, or would take to long for the 12 minutes the dwarves have before the fight begins.
Also, arrows are non-craftable items as the regenerate in your inventory over time.