Northlineexperss.com is one place I found on the web that has lots of info and seemed reasonable. Any place locally to me had to order the couple of pieces of flue pipe I needed, so I just ordered it myself. I found a telescoping section of flue pipe, 44 to 68 inches, was a perfect solution to adding the stove pipe length I needed and allow for flexibility in positioning the heater and chimney thimble in the wall.
My heater came with DuraTech double wall Class A chimney and DuraBlack stove pipe.
Charles