There are many varieties grown in Britain, but where can they be bought in the USA?
I am sorry, but I can only offer information on growing these plants and not where to source them.
I can offer a collection of articles that will help you to grow them, however:
https://www.gardeningknowhow.com/edible/vegetables/rhubarb
Also, please do not include your personal information to the public. I will remove it this time, for you.
After the mild winter mine is tall and looks ready to cut.
You can typically harvest rhubarb stalks when they are firm, thick, and fully grown, usually starting in late spring or early summer. It's best to wait until the second year after planting to allow the plant to establish itself fully.
Avoid harvesting more than one-third of the stalks at a time to ensure the plant remains healthy and productive. Additionally, avoid harvesting rhubarb stalks once they become thin and begin to droop, as they may become fibrous and less flavorful.
https://www.gardeningknowhow.com/edible/vegetables/rhubarb/harvesting-rhubarb.htm