How tall would the bamboo need to be?

You'd be better off planting sunflowers or castor beans for a quick cover and planting a fast growing tree. That's not enough space for any bamboo that will get tall enough to shade a bush.

I would recommend a clumper if kept in a pot, and in your zone you could go with a number of bamboos, especially if you are planning on bringing the plant indoors during the colder months.

Several of the bambusas would do fine particularly the Bambusa multiplexes. B. mult. 'Silverstripe' is one that leans outward a lot so it would give excellent shade for close neighbouring plants. In a pot the size you described, it would probably grow to 12 or 14 feet max in height, so it wouldn't be too tall.

In full sun, it gives dense foliage so it is a definite possibility.

Are you planning on having more than one pot?

Kt

Thank you all for such quick response. I will try the Silverstripe in a larger tera cotta pot -- 10 - 12 ft is all I need. I will also plant some sunflowers in the converted canning pot for quick shade.