Thanks for the well-formed question.
For something like that, I think that WonderFlex
or Craft Foam
would suit your purposes best. It's a simple curve, so what you would do is cut the shape out, curve it, and then strengthen/smooth/paint it as you see fit.
If you want to make the moon and holes (are they holes?) look kind like they're embossed in there, you could simply make two layers. Curve them first, then cut them out. If you bend them first, it assures that they'll line up when placed on top of each other. It makes accurate cuts trickier, but you could make a paper template to guide yourself. After they're cut, set them apart. Paint the bottom one black, cut out parts of the top one and paint it red. Attach them with some glue, and you're set.
Should work out, let's see what other have to say.