When all else fails, you could get an ITT Products sound module, GL520...
It'll run for about 30 seconds at the push of your accessory button. If the Lionel speaker is 8Ω you should be able to use the same rather than provide your own. Anyhow, wiring it to the same push button and accessory power, you'll have your beacon light and a great seashore/foghorn sound to complement.
Just a thought...
KD