There is a cuban store in Shanghai's Xintiandi area that sells cuban cigars.

buddy, if i were you, i would be careful to buy any high quality things in china, they might sell you the fake stuffs for the original price!

Cuban cigars are sold at many places throughout China.  Many large cigarrete stores carry them, in some major cities, there are specialty stores selling only Cuban cigars, but I will njot buy from any a closed box without inspecting each cigar.  If they feel hard to your touch, they have dried and become brittle, will burn too fast.  You can fix that by placing apple slices with the cigars in a close box for a day or two.  Or some even I have found with worms inside, you will see that if full of small holes on the surface.  Stay away from those.

Cuban cigars are good, but so expensive, that to buy a box of 25, and find a few no good, it is a painful experience.