To get a ground throw to scale in N scale it would be quite small. There are some alternatives that I know of though.
If you're willing to mount your throw remotely you could look at Hump Yard throws. They are quite nice.
If you want an on-site throw then you can make something that will work pretty well pretty easily, though it won't help you with flipping polarity if you have a live frog. Check this out: http://www.telusplanet.net/public/crowley/ground_throws.htm