Where can I get this or is it a custom, one-of-a-kind thing?
Sure, here's what it does.
it's a set of mults and attenuators
it covers all inputs/outputs of the MiniBrute (Audio and CV)
it adds attenuators for VCA and VCF input on the MiniBrute
it's completely passive
There's a MW thread as well http://www.muffwiggler.com/forum/viewtopic.php?t=108849&start=0&postdays=0&postorder=asc&highlight=