Where can I find a flange to attach to combustion fan intake

I want to duct outside air to my LL Pocono intake fan. It's a pretty easy install, however I can't seem to find a flanged 3" or 4" piece which will attach over top the intake fan area.

Would appreciate any input on what you all have used? I check with Home Depot and Lowes, but didn't see anything that would suit the task.

Thanks!

People have used 3" starter collar. You can cut 3/4" slits around the pipe & bend the tabs out. Drill holes in 2 tabs that line up with the screws on the fan, remove screws & attach pipe. I just made 2 "L" brackets attached them to the fan using screws on the fan & slid the 3" pipe over it.

Quieter is better...


and


http://www.hectorshardware.biz/shop/pro ... ku=436682&

that is a 4"collar...I bought a 3", but the guy at the parts house called it an "A" collar or something similar. My tabs looked like the letter A.

I haven't done my combustion blowers yet, but on my convection blowers, I just cut and bent tabs to use existing mounting screws.

I did find the starter collar in a 4", but not the 3", I'll have to check out some other places for a 3", that will do the trick! Thanks!