It is easier than you think.
It is just some tubing that you can likely pick up in bulk from any hardware store. Drill a hole in the top of the cooler with whatever size hole you need to fit the tubing through. Shove the tubing through the hole far enough so it reaches the bottom and put something on the hose on the inside of the cooler cap to keep the hose from pulling out. If you can't find anything rubber, you could just put a stainless steel hose clamp on it. Just need something on the inside of the cooler to hold the hose in there. The plumbing is the easiest part. Mounting it is the hardest which is where his kit is nice. Not impossible but way harder than drilling a hole and stuffing a hose though said hole.