This guy has what you need. It is a special fitting for the Setrab has an o-ring. They are only about 13 bucks each, Monty also has all the hose and ends you will ever need,, prices are good too service is top notch.
Or you can do like I did- drive around for two weeks trying to reinvent the wheel and almost screw up your 300 buck cooler.
Monty Holt
Bits & Pieces
(562) 420-3557
Bits & Pieces Motorsports - Hardware and Supplies