Lionel made a scale GP7 several years ago. I can't remember if it was 'Polar Railroad' or 'Polar Express'.
I've got one. It says "Polar Railroad". I have all of the Polar Railroad (with a few duplicates) and most of the Polar Express scale freight cars. I have one caboose each Polar Railroad / Polar Express.
There is one on eBay now. Do a search for "Polar Railroad" gp7