I took measurements of one of my cousin's pop-its that she's always playing with to make custom ones out of silicone. Once I modeled it, we had a fun joke about printing it and having a hard plastic pop. So you can print the pop as a gag or use the other files to print top and bottom molds to cast a pop-it in silicone. As of now, I've just finished optimizing the pop dimensions so I only have the single but I will be using it to make many custom designs. 

The pop will definitely need supports but the molds will not, just be sure to lay them flat. I use a 0.25mm nozzle with 0.05mm layer height for best resolution along the bubble, but change the layers to 0.15mm for everything else. There are holes for 3M bolts and a hex nut to fit on one side. Make sure you puncture the sacrificial layer first, then use the screw pull technique ;) to seat the nut. I've been using Mold Star 20T with a scoop (from a scooper I modeled and printed, so I don't have a proper volume) of cornstarch, a scoop of mica powder, and a single drop of paint to 5g of silicone. I'm still perfecting this technique.