Well you could always port over one that was from a den, then give it Dynamax Candies afterwards.
As for Gigantamax Charizard, I suspect that that you'll have the same issues as well, and even worse, no items can make a mon giganta-capable.
I'm saying it is unlikely. If you know which byte (on the hex file) is for gigantamaxing and dynamax level,
you could try editing the same address on a gen 7 hex file, then import that.