Hey Dino,
Welcome aboard! Are you asking about the bell sound or the bell itself? For sound, how about a continuous loop tape recording of a bell that could be activated by a switch? I recorded a bell sound like this off of Microsoft Trains Simulator to use for the facsimilie control stand I use to run my layout. I have the continuous loop tape in a cheap walkman with an insulated copper disk between the batteries, interupting the current. When I move a switch it opens this circuit, letting the walkman play through small speakers, simulating a locomotive bell.
Ralph