Lionel has a new line of Standard Gauge Trains that will run on 2 inch plastic or metal 2 or 3 rail track.
They call them Ready-to-Play trains sets.
They replaced the older G size sets and added new styles.
They are very cheap about $100 list and $50 + shipping from online sellers.
I brought one set for $45 to see if I can get it to run on powered standard gauge track by adding pickup rollers and electronics to convert to 9 volts dc.
They come stock as "dead" rail with 6 C cells in loco for weight and power with a remote-control controller.
A UK garden mag has a article on how to covert them to G gauge track, but it is a lot of work.