Adafruit
https://www.adafruit.com/
Amazon.com
https://www.amazon.com/ideas/amzn1.account.AGITJ246IQAKYEU5NUMG3N2AT4OA/2J4WYCKBBSW92
Brown Dog Gadgets
https://learn.browndoggadgets.com/
Chibitronics
https://chibitronics.com/
Kitronik
https://kitronik.co.uk/
Makerspaces.com
https://www.makerspaces.com/
Sparkfun
https://www.sparkfun.com/
Squishy Circuits
https://squishycircuits.com/
STEM Education Works
https://stemeducationworks.com/