Instead of selling fireworks magic in the future can it be a reward for winning a certain amount of fireworks games? It used to be obtained for hitting a certain score in the original game and when remixed came out the gold remix pin was awarded for winning 10 games. This would make it a challenge to win the magic pin over just being able to purchase it.
I'm assuming that fireworks magic will be released in a similar fashion as you suggest. It's related to the game, so it makes sense to release it in such a way.
There is a slight clarification to what you stated regarding how the original fireworks game awarded the magic pin (as well as how to obtain the gold pin in Remixed):
It wasn't that you had to obtain a certain score (I think the first pin you got was this way), it was that every ten games that you had at that score garnered a Fireworks Magic Pin. To obtain the Gold Pin in Remixed, you had to do the same thing - achieve a specific score ten times. To do so in this version would make sense to me!