Hull Hugger Muffler

If you have the muffler, a welding fabricator could make you a Y pipe that fits in it's place with existing hoses.
If you dont have the muffler you can fabricate what you need from pvc pipe and just about any welder fabricator can reproduce it for you.

You can piece something together from centek (see link)
https://centekmarine.com/products/exhaust-systems/

If you have the muffler and it is leaking you could repair it, there are endless possibilities depending on what you have to work with, time, money, parts, skills, how hard does your wallet open is usually what it comes down to and on and on.

Just don't don't ask what what it's worth or if you should bother registering the trailer.
Ha!