Well, I haven't quite obtained all of them yet myself, but I do have a couple more than you:10-14. Souveigniers.
These are obtained by taking your Tamagotchi on one of the five plane trips. Tickets are available in the shops upon occasion, but the price is dear. Don't buy the same one twice! Once your Tama's taken the trip, a password will come up. Put the password in at Tamatown's Travel Agency to obtain the correct souveignier.28. Bandai Medal
To obtain this, you have to go to the Tama Mall, and then into the Toy Store (center). You will see a Memetchi and Young Mametchi playing with a racetrack. Click on the racetrack to play the game. Win, and you will receive the medal.
Sorry I can't give you any more help, but I don't really play Tamatown that much, so this is all I got.