Available as an assembled Module and as a DIY project.
This Module is currently available.
CGS 202 / 522 Serge Resonant Equalizer module / panel in LW format
CGS 202 / 522 Serge Resonant Equalizer module / panel in LW format
https://www.elby-designs.com/webtek/cgs/serge/cgs522/cgs522.htm
http://www.loudestwarning.co.uk/portfolio/cgs-202-serge-resonant-equalizer/
These merchants probably sell this module. Huh?