Thanks Jim. The Marx with bell is really really tall. I guess if I could find one that is totally trashed, I could salvage the bell on it. But, I would hate to destroy one that is even in just "good" condition.
There is a company that sells a small bell sound component unit, with a small speaker, that can be added to just a flashing light crossing, but it is for HO only, so it is DC powered. I have a bridge rectifier, so maybe after I hook up the Marx Stop-On until with AC power wires running to its screw down posts, I could try hooking up a separate set of feed wires, running away from the screw down posts over to the rectifier to convert current to DC, and then to the DC powered sound unit. But, I would hate to try this without knowing it would work, because that sound unit is a good $50 or more.
It would be easier if I could find an AC powered bell sound unit and speaker, but I haven't been able to find one. Not sure if anybody sells them.
Mannyrock