Available as an assembled Module and as a DIY project.
This Module is currently available.
hands on acostic interface
color your eurorack system
3 hp guitar spring tool in eurorack
passive
comes with 4 replaceable springs and different sound
see demo
hands on acostic interface
https://www.errorinstruments.com/a-53377378/new-on-error-welcom/raw-spring-nano-colors/
These merchants probably sell this module. Huh?