Dahon normally doesn't sell parts (to consumers), distributors may have some but not many. That's why Dahon copies (Litepro, Fnhon) are so popular in China. Aliexpress (for people outside China ) or Taobao (more for people in China) are basically where you can buy these parts. As for the quality, I have used some Fnhon and Litepro as well as Dahon, there is no noticeable difference. These copiers even make improvements here or there. And these are bike parts not rocket parts, it's actually very had to make a bad copy