My wife pointed out to me about a mini program on Wechat that you can use in English to show proof of vaccination. Here's the article. It's in Chinese. It tells you how to fill out the program. I didn't see a 'English version' button so many someone could point it out where it is (if there is one).
mp.weixin.qq.com/s/4yMYnuA4-Xjwiwsc4oFv1A

I believe you'll have to print it out in paper format.