The banner is from Michael's—sold in the baby shower aisle. I noticed that many of the letters were already the same. There was an H-A-Y for the word Happy and I could make the B's into P's pretty easily. The W turned upside down looks like an M and the H is easy to make into a U with some extra card stock. You get the idea.
The pastel colors of the baby shower banner didn't work for Purim so I painted each letter in bright happy colors like orange, turquoise and lime green. You can find the instructions for the pom-pom Purim groggers here.