The geometry of the tubing is the same between the Burly and the Primo, so a Burly mounting plate can be mounting on a Primo. A more complete answer can be found in this topic. If are eyeing a specific needle cutter designed for the Burly, I’ll take a look and see how much work it would be to modify it for the Primo.
If you go down the Burly mount route, it can be a pain switching mount systems between the Burly and the Primo. One solution is to build a second Z axis using the same model stepper motor. Then you can just slip out one Z axis and slip in another one to go from routing to foam cutting.
Edit to add: I’ve never implemented a needle cutter, but out of curiosity, I’ve read many of the topics concerning needle cutters. In one post I saw something like, “I tried cutting Dollar Tree foam board today with my router and a 0.8mm bit, and it worked really well.” So, if you only have a few replacements parts, you could try cutting the foam with your router.