I don’t know the brand alas. I copied the Chinese characters from the AO3 fandom tag and plopped that in the Taobao search — actually I used Baopals, which is an English language version, and scrolled thru the Guardian merch. I also bought some keychains. There is ... a lot of stuff, but if you have time, you should totally scroll through all the stuff.
Oooh I will also check out that link!