I gave a talk recently at a gathering of Shortwave radio listeners. I decided that I would demonstrate the "Internet" as part of my talk so I set about building one of my own. It's incredibly simple and requires just a few $$ of parts and a black plastic box.
My boxes had a 9V battery for power and the circuit was stuck onto the inside of the lid with double sided tape.
It you want to make one of your own you can buy a board from Oshpark
As usual, here are the files in Eagle format along with GCode for your CNC mill ...
555 Internet Flasher.pdf
555 Internet Flasher.sch
555 Internet Flasher.brd
555 Internet Flasher.bot.etch.ngc