Speaking of eBay, there's someone selling a Lemax Toy World with "no movement."
Is the "lid" to the can welded or can it be removed by bending some tabs or whatever? It appears the 49TYJ motor comes in various voltages and speeds. So if you can't find the exact 12V 6 RPM model, I wonder if you can mix/match parts.
For example, I'd think a plastic pinion gear on the motor shaft in the center of the can could crack/fail and could be replaced. This is probably the most common reason O-gauge crossing gates stop moving. If you turn down/off the sounds can you hear/feel the motor spinning?