The Gigantamax forms of these two Pokemon were introduced in the Armor Island DLC after the player completed the first footprint of the Dojo Master. To save game time, you can choose to buy 6IV Shiny Ditto. If you want to add them to your collection, just go to the mystery gift option in the sword or shield game and choose to get it via the Internet. But now players who don't have an expansion pack can score for themselves.
Players who use the DLC to obtain one of these entry Pokemon can use this mysterious gift and the Charmander, which is given to the player after completing the story, to collect all three entry Pokemon with the Gigantamax factor.
If you plan to score one of these Gigantamax entry Pokemon, I recommend that you can Buy Shiny Pokemon now, because it is not clear when they will be offered again outside of the DLC.