Evil Mad Scientist makes a giant, discrete version as a soldering kit:

https://shop.evilmadscientist.com/productsmenu/tinykitlist/6...

Very cool. (Looks like it uses 26 transistors. I assume the die is similar.)

I believe they based the design off of the reference schematic from a datasheet of one of the popular 555 timers, but I don't remember which one.