Have you thought about building your own? It will be a really simple exercise in modelling.
Two frames of approximate dimensions, a couple of spacers in the right places for the body mounting, and add motor and gearbox to taste. Springing or compensation are optional, but would add smoothness and reliability to running.
The key is that the side skirts hide all manner of mechanical sins. This is the Crude But Effective chassis that sites beneath my tram:
And from underneath, showing the simple pickups:
And this is what rides on top, completely hiding the crudeness of the mechanics:
Give it a try – you’ll be surprised how easy it is.