Where do you guys buy your Lipos online? (North America)

As the title implies, where do you guys buy them? I need 10s in total, but hobbyking is always out of stock in 5s, and their 10s lipo batteries just aren’t worth the price tag. Banggood also carries lipos, but third party companies I never heard of, and the same goes with ebay. Should I just do 5 x 2s in series to get myself 10s? If so, how do you guys wire all of those in series?

Thank you.