I must say finding a used one is going to be next to impossible. Furuno doesn't make them anymore.
This one is still made and will work with the FCV1150: CA50BL-24HR, FRP Transducer (BLT), Type 50BL-24HR, 3kW (No Plug). With this one connect it direct to the FCV1150 **DO NOT USE the BT-5 Booster box)