I want to install a fresh air intake on my Pellet stove but the kit from the manufacturer (Quadra Fire) cost about $100 which is outrageous. Even the dealer said "make it yourself". I can find the parts to to this myself with the exception of the aluminum flex tubing. I need 2 inch and cannot find anything under 3" that is not part of an expensive kit. Where should I look?

thanks, Rick.