Paulo - Have you seen the Hacker cryostat.  They have a portable cryostat
that can be carried in the back of a car.  It has been used quite a lot by
pathologists who do frozen sections at many hospitals.  Hacker Industries is
in New Jersey but also in Europe so you should be able to find a vendor.
Cheryl Crowder
LSU Sch.. of Vet. Med