I often visit the Electronics Flea Market held on the second Saturday (starting at 5:00 AM for no reason) of every month, March–September. I often buy things very cheaply there, and resell them on eBay.
Here are some of my finds (two trips out of 6):
I have no idea where they get these things or why they are so cheap, but they should sell more of the same.
Also, it’s really tiring to carry lots of stuff for hours at a time, as I’ve discovered.