I am not exactly sure what the porcupine structure is (but can imagine), but this is something inexpensive I used in my pond. 5-gallon bucket, 1 bag of concrete, paddle bit, and leftover irrigation poly tube. Ended up with 3 of them in the pond. They do get pretty heavy and tricky to place. Probably get away with just adding enough concrete to lock in the poly tubing and call it good.
