https://reverb.com/item/60482030-alembic-f-1x-tube-bass-preamplifier-preamp-rack (https://reverb.com/item/60482030-alembic-f-1x-tube-bass-preamplifier-preamp-rack)
Seems pricy, but condition looks good and seller has solid feedback.
Well, they are $3300 new and on back order so...
GC in NY has one for 900 bucks
https://www.guitarcenter.com/Used/?Ntt=alembic&Ns=r