Years ago I used to pick up bamboo at Pier One Imports or World Market stores. They used to sell it in 5 or six foot lengths in the diameters you mention. I use it for curtain rods. But since the accidental import of the Emerald Ash Borer from Asia to the midwestern US those imports may have slowed down.
If you are in or near a major city with an Asian population there also may be small shops that would import bamboo for decorative purposes.
I'm sure some research would lead you to a way to devise a hand tool to ream it out. They have been doing it for centuries in many cultures. Though the "by hand" thing sounds pretty labor intensive. Reaming out a piece of bamboo is a heck of a lot easier than boring a length of blackwood, but it is still going to be labor intensive.
