WTB: Sage Model B Netto Total Energy Box

Would like to purchase a functioning model B Sage netto total energy
box, calibrated for gliders with L/D of 40:1 or greater, to mate with
my Sage CVA vario. B model "boxes" have a serial number printed on the
face of the unit which starts with the letter B. I am also interested
in obtaining poorly functioning models, to pull apart, reassemble and
possibly get a functioning model completed. When they work correctly,
they are unbeatable.