Try checking with local companies that use stainless pipe. They may sell sections to you as scrap, or just give it to you.
Where I work, they use t304 or higher grade 2.5-12" pipe. I got all my 2.5 and 3" for free. The 3" I got was an 8' section, and a 3' secction with a 90deg bend at one end....all with v-band flanges.