I didn't know that there were aftermarket tips for those, but I found
one on eBay that looks custom fabricated.
The tips have a lip that fits into a slot on the muffler and a single bolt that clamps it in from the bottom. Easy to remove or swap out if you have one that is made or adapted to fit the same way.
Stock 2.7L version:
I'm not a very good welder/fabricator, but I could probably slag one together pretty easily. A good muffler shop should be able to handle it if you have a tip and explanation.