I've used a more common LM13700 instead of LM3080.
You can find original project and scheamtic here.
I could not find any videos for this effect but there are some sound samples available here.
The original effect uses a momentary SPST footswitch.
I've also added an unverified true bypass version.
If you don't want the External Trigger just remove it and connect Thresh 1 to LM308 pin 2.