I believe you can find these things at Decathlon, located opposite Ikea in South Chengdu. You could find much more variety and maybe better quality (not sure of Decathlon’s offerings in this department) shopping online on JD or Taobao, if you can find a friend to order them for you.
I was going to recommend Decathlon also. You can definitely find everything you need online at JD but Decathlon is pretty good. As good as you will get at a retail store in China, probably.