I got the tarp and fittings from topcanopy.com but I'm not too thrilled with the wall thickness of the tubing they used on teh fittings and some of the welds are just really bad.
I ordered some parts from tarps.com in the past for building a big outdoor movie screen and they were higher quality. However, their 1-3/8" fittings don't have set screw eyebolts like the 1" EMT ones do.
If you go with 1-3/8", HD has the cheaper and better fence poles because they're 17gauge. Lowes has 18 gauge which is thinner. I had to go to a fence supply for the three 14' pieces but after putting it up, I'd recommend keeping spans to 10'.