Tidbit Audio make passive utilities, attenuators, mult-switches, switches and other nifty things to use in your modular setup. And the cool thing is that they don't take up any HP. Some can be fed with CV to power in built electronics to provide a variety of widgets, doodads and sound generators.
Really cool. And they make some cool specialist microphones as well.
https://www.etsy.com/shop/TidbitAudio
Older Music Machines & the People Who Still Use Them