If you ever come to Huaqiang Bei Shenzhen, you will see a lot of electronics markets. And a lot of the markets are built just for the makers like you who design things, build gadgets, and so on. However, from my obversation over the last 10 years, I can see that this business for the parts and components is dying from Huaqiang Bei, it does not mean that there are less and less makers, in fact, there are more and more makers that come to Shenzhen, but a lot of them are just buying parts from Taobao.com,
Since 2013, more and more 3D printers come to the market, some of them build nice shop in new Huaqiang Markets, and they show you what they can print.
The picture above show you what a 3D printer can do, print a bra.
For overseas makers, you want to see what is available and you can grab the parts right away and go back to your hotel or office for testing to verify your idea or to test the parts and if the parts are not good you can just go back to get a replace one, however if you get the parts online, you need to wait, it might be a little cheaper on Taobao but you will waste your time on the developping process.
Here is an interesting video that you might like on Youtube.