Technically you're not going to be able to purchase a KISS in Europe wether it be new or 2nd hand. Due to the CE issue on the unit, whoever was the seller would be classed as importer and therefore potentially liable for the outcome of use of the unit.
If you were lucky enough to buy a bag of bits for the mantlepiece that once formed a unit, then I believe that's a different kettle of fish, but you won't be able to buy a non CE rebreather.
If you did find said bag of bits, and you didn't want them, then I might now a man who will. Say no more!!
hth g.