Usually when Joshua Jay's tricks are released (Prism, Inferno etc), or any other author/developer not directly affiliated with PM, to get the refills, you'll have to go to their representative site...in this case, Vanishing Inc Magic.
To save you some time, here's the link for your refill.
https://www.vanishingincmagic.com/magic/card-magic/prism-refill/
PM will rarely redirect you there.
Best wishes