WARNING: Do not sell any materials! If you happen to sell any one time materials then this achievement will become missable and you will have to restart.
You acquire all battle items by ordering them from the Item shop in Konoha. As you progress through the game more items become available on the order list. There are a total of 48 different battle items in the game. Make sure you pick up EVERYTHING during your main playthrough to ensure you have all the materials you need to make everything. Some materials however, can only be obtained through requests.
5 particular materials only appear in a special way. Viper Fang is a bonus condition for the Sasuke vs Killer Bee (Transformed) fight from the Fragment Chapter in the Hokages room. The other 4 materials are:
New Moon Flower
Leaf from the tree of life
These materials are obtained after certain chain letters that you get after buying these books from a merchant, to find out more about those books refer to "Ninja of Letters"
Complete List of Battle Items