The Steel Teeth are found in the hall that's before the Deep Colosseum. You'll need to go to Snagem Hideout a second time (After you retrieve the last Starter from the last Color Peon in the Shadow Pokémon Lab.) and beat Gonzap there. As he leaves, you'll find the D-Disk, which will take you to the Deep Colosseum in The Under. In the left, just before the big Colosseum's door, you'll find the Steel Teeth.
The three Time Flutes are:
1st: Vander gives one to you after you beat Dakim in Mt. Battle.
2nd: As you use The Under's Subway to get into the Shadow Pokémon Lab, go to the right of the entrance of the Lab (The one the Peon blws up.). You'll find a small room where you'll find the U-Disk. Use it in The Under's UFO, and you'll get into Pyrite's Windmill. A chest there contains the second Time Flute.
3rd: You must reach the 100th Trainer in Story Mode's Mt. Battle. Before getting into the platform, you'll be standing in a rectangular staircase. Go to the rightmost part of it to find a chest with the last Time Flute.
Hope this helps.
