Peter,
To answer your question by saying yes. Here is a picture of an N scale refinery.
These are called Pico size LED's, smallest I have seen. They are 3 volt and operate (as many as 50) off of one regulated 3 volt wallwart.
I have no interest in the sale of these by any vendor so check out (
http://www.modeltrainsoftware.com/ ). These folks are excellent to do business with, check out all his LEd's.
You might try Mike and Robin Fifer as I know they had some of their items in stock at one time. Richmond Controls may have something comparable as well
I hope thre is some helpful info here for you.
Always, have fun!
Carl