Hong Kong and Shenzhen are mecca for hardware enthusiasts. In my previous blog post I shared about buying Arduino in Hong Kong. Let me share some more information about sourcing electronic components in Hong Kong and Shenzhen.
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The Scoutbots projects aims to explore and protect the Oceans with Open Technologies. They maintain a comprehensive list of material suppliers in Hong Kong and Shenzhen here https://sites.google.com/a/scoutbots.com/wiki/home/references/material-suppliers-in-hong-kong-shenzhen