I bought my Dwarf Cavandish from Stark Bros. catalog. They claim the plants shipped will be 6 to 12 inches. $11.00 a plant or you can pay more for a kit that includes the plastic pot. The plants looked a little weak when they arrived. I called and explained what they looked like and the nice rep explained that if the leaves look a little "iffy" but the pseudostem is green, plant is fine.
Sure enough, they survived and look good even with wintering indoors (PA.). Soon I'll move them outside but they made it thru the winter with just enough light. Warmth came from a coal stove.
Link below.

Here is a link that might be useful: starkbros.com

Thank you. I will check this website out.