I've been using my Shoebox as much as possible lately , and with the cold Pennsylvania mornings, I realize I need to hook up my defroster vents to help keep the windshield clear. Do any of you guys have a source that you've used to buy this stuff. Can be either cardboard/paper or plastic. The Shoebox uses 1 3/4" i.d. tube , BTW. I checked at the local parts joint, no luck. I just did a quick internet search, and came up pretty slim. Maybe I'm not calling it the right stuff ? I realize a lot of you guys remove your heaters, or think they're not traditional out whatever, but i use the car quite a bit, and here on PA at this time of year you need a heater in a closed car- even a custom . Can anyone point me in the right direction ? Thanks in advance !