You can either find this item or make them. This is one of the methods to make them using a Tetradic Tiara. Follow the order exactly. Also, this works best if you have the accessory that makes you more likely to get a drop after a battle. Make sure you upgrade it to the top tier as well.
1. Buy Four Iron-Bangles (500 Gil each)
2. Make sure there are no Tetradic Tiaras in your inventory.
3. Repeatedly do mission 7 (Disc 3, Gran Pulse) until you get the rare drop of a Tetradic Tiara.
4. Save the game.
5. Break down all four Iron-Bangles.
6. Upgrade Tetradic Tiara level 1 to Tetradic Tiara ? (only one level till star).
7. Break down Tetra Tiara ?
8. Repeat the steps as desired.
The result should be one raw material that sells for 12,500 Gil, three Talisman and one pair of Sprint Shoes. You can do the same process if you get the drop of Tetradic Crown instead of the Tiara, however instead of breaking down four Iron-Bangles, just break down three. Also, instead of getting the Sprint Shoes you'll get something else called Herme's Shoes. If you upgrade this to the star level (just one level) then upgrade it with the correct crystal/stone/etc., it will turn into the Sprint Shoes. Alternately, you could take the Tetradic Crown, upgrade it to star level, then using the correct stone/crystal (Mnir Stone or something similar) you can turn it into Tetradic Tiara and do he process above.