The Winged Dragon of Ra can be found in Yu-Gi-Oh! Magazine (check the calendar). Obelisk the Tormentor can be found in the green Millenium-puzzel booster pack. You can get that booster pack by beating stage 4 10 times. If you are using an emulator, save before choosing a booster pack. If there isn't a useful card in it, load again. (for the VisualBoy Advance use the F keys)