Get one done locally. It will only cost around $300, and I would get an larger o2 housing but it isnt really nessecary. They dont need anything. They can open it up from the o2 housing to a full 2.5" or 3", whatever you app. is, and run straight pipe all the way back to a perforated muffler.
If they say anything about needing a cat you can say its an off road only car you can buy a high flow cat .
My buddy took his brothers gt42r civic to a local exhaust shop and got a full 4" aluminum exhaust with v band clamps for only $700!

Thats a steal! Im thinking about getting an aluminum exhaust done there to in the future.