Vactrol PiLL (Modular Addict Panel)
This is a simple circuit that is capable of making a wide variety of sounds. With a sequencer it can be used as a crude VCO, but fed other signals, such as from envelope generators and LFOs, it will sound like anything from a baboon with the squirts to a cheesy 80s video game laser cannon.
http://nonlinearcircuits.blogspot.com.au/2015/02/vactrol-pill.html
http://modularaddict.com/nlc-vactrol-pill-panel
Module is available as a DIY project only.
No info about availability.