Longer upper shaft for Excal 2?

I am looking to elongate either my lower shaft or upper. Being 6'7 tall isn't quite working out with the stock excal shaft. I searched Home Depot and Lowe's for aluminum tubing and couldn't find it in the raw metal section or the electrical conduit section. Where can I get the correct diameter tubing in person? Id like to see it before buying which is why I prefer not buying online and I really dont see the ROI of paying Anderson over $100 for 2 pieces of $5 aluminum tubing. Any help would be appreciated thanks!