Answer: Keep in mind that even clumping forms can gradually grow quite wide over time. Your size range is actually very small in terms of bamboo because bamboos as a rule tend to be large plants, more like trees than shrubs in size. I wonder if you might also consider using an ornamental grass instead, as this might be more in the size range you have in mind.
The most popular hardy clumping bamboo for small spots is probably Fargesia, however unfortunately it will not grow well in areas with hot summers and high humidity and also needs afternoon shade. So this would not be a good choice for you.
You might look into Bambusa multiplex `Golden Goddess` which seems to meet your criteria quite well with one reservation: your zip code places you in the warmest part of USDA winter hardiness zone 7, so depending on your microclimate it might actually be as warm as zone 8. This plant is considered winter hardy to zone 8, so please check with your local nursery to see if they think it would grow well for you, or not. If not perhaps they will have a substitute to suggest.
There is a zip code based dealer locator at the Monrovia web site; Monrovia plants are sold by independent retailers so you would need to check with them directly to see if they have it in stock or could obtain it for you.
Best of luck with your bamboo!
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