Unfortunately, your Zone makes growing bamboo a challenge, and most of the clumping (non-invasive) species are not as hardy as some of the running types. The best I can suggest is to get one of the Fargesia varieties, a number of which are supposed to be hardy to minus 20F. That doesn't mean that they'll keep their leaves or even, perhaps, their culms in winter, but the root system should survive to that low of a temperature unless you have a sustained cold spell.

snoop around here:

http://bambooweb.info/SSL.php

I suggest you get a BIG, deep container on the order of the diameter you want for your clump, and choose a running bamboo.

Two clumpers, Fargesia rufa and Fargesia robusta could be worth a try. Even though running bamboo are funner.

Don't be discouraged by other responses. Fargesia are very beautiful and will THRIVE in zone 6. Just note their needs: a little shielding from wind and sun. Think rhododendrun. And then there are a handful of runners out there too, ya just gotta think containment.

Often grow with rhododendron and spruce in the wild.