I have exactly the same circumstances as you. Also a Turner-era Series I, with intermittently dodgy electronics. And occasional high-pitched squeals with the Treble Q control in the Max position.
I've also been looking for alternatives to address the issue, and the purported $1200.00 price tag is really tough for me to rationalize.
I will be very interested to hear what you find out from Mica and/or whether you have success with the BoogieMan.
These mid/late Seventies Alembics are incredible instruments, but I find myself too often grabbing another bass that has less temperamental electronics. I tried to use my Series I for a show a few months back and the ancient jury-rigged wiring in the building did not get along with the Series I at all. Wound up grabbing a passive bass to avoid the noise.
Thanks for posting to the forum and keeping other players informed.