If you guarantee good quality, save time and effort, and don’t mind the price, buy them at scenic spots. You can buy them at Dongzha and Xizha scenic spots, and look for ones with a relatively large scale.
Of course, if you don’t care about time and energy, they are sold in more remote scenic spots or in shops on nearby streets, but choosing a good one depends on your discernment.
Specialty products are just pictures with special characters. Nowadays, some of them are sold on Taobao, and they are not expensive. The key to traveling is to have fun.