If you go to Taobao (
www.taobao.com) and search using an English-language brand name or copy-paste "折叠自行车“ (folding bicycle) into your search, you can quickly get a view of what's available at what price in RMB.
So equipped, I'd then just go into random bike shops in Guangzhou and look for something that fits your needs. Plan for a close inspection of the individual frame. There are good products available but consistency is sometimes not there from bike to bike.
I agree with earlier posts that the low-end has the better bargains -- often with decent components from the low-end of name-brand groups. I would also do a complete disassemble and reassemble when you get home to make sure everything is aligned, correctly threaded, tightly assembled, etc.
Good luck hunting!
yes. that's the site where i buy some stuff for my bikes but i have an advantage in a way that i know a local guy who usually do the transactions for me and i know someone who brings them back for me here in usa. win win for me as it is cheaper and free shipping.