.co.cn or .co/zh-cn - have you worked with a sub folder structure in China?

I have a situation with a client whose site (multilingual) is migrating to a new domain, and its a .co We recommended that they go with a .cn domain for China. However, the cn domain same as the global tld is not available. What is a good solution in this case? Have you worked with a sub-domain or a subfolder in China? Did it work well? How was the visibility?