This product is called Missingno Egg, also named Gold Egg.
After you get this egg, you will be able to clone hold items unlimitedly, easy & fast, and it is 100% safe.
Since this is a small glitch in the current game version, we don't know when the game will fix this bug, for now this method still work until the next game update.
If you are still worrying about don't have enough hold items, this method is suitable for you, you can easily get enough hold items in a short period of time by using Missingno Egg.
Note: Trade Missingno Egg requires a computer, contact our customer service before purchasing.