I got my flanges from keating machine, while they may not be the cheapest they are top notch quality products with great customer service! I also used 3" schedule 40 pipe for my pipe as well. I actually happen to have a few left over elbows and a section of pipe as well if you don't have a source already. Just as a heads up the short radius 3" schedule 40 elbows are hard to come by and very pricey. If you have any more questions or are interested in pipe you can pm me.
Tyler