https://hackaday.com/2024/03/13/review-the-new-essential-guide-to-electronics-in-shenzhen/#more-668397 

Jenny's review brought to mind an older SolderSmoke blog post about Shenzhen. In this 2012 video  Bunnie Huang in Singapore talks about getting parts in that city: https://soldersmoke.blogspot.com/2012/08/singapore-knack.html

Thanks to Jenny, Naomi, and Bunnie.