If you don’t know what AliExpress (https://www.aliexpress.com) is, wherever you’re buying your stuff from, you’re probably paying too much. The best way to describe it is with an example.
The gimmicks in this picture are USB LEDs that light up when they are inserted into a USB connector. They turn any USB power source into a lamp. I bought them from AliExpress in a pack of 5 for US$ 0.68, postage included. Ridiculously cheap.