I reckon you should do it yourself. Pick up some mandrel bends and straight sections of steel in the right diameter from an exhaust joint. Drive round and have a chat, some let you have them basically free. Then spend a bunch of time cutting bends and holding them in place. Mark the joins and then tack-weld them together. Check it still fits and then move onto the next piece.
Eventually you get a set of intercooler pipes. Then take the set to a good welder who can do the final air-tight welding. remember to put some flexible pieces in and also that you actually have to be able to slide all the sections into place.