Years ago, I created some flashcards with trains and letters on them. This was an effort to teach my child to sound out words by building trains. Today he is a fantastic reader! I finally made better (hand-drawn) versions of the trains and have printed them on flashcard paper produced by Avery. I am getting ready to set up an Etsy page so that you all can purchase these if you like. I will link to it here when it is ready. Note: the caboose and engine do not have letters on them, however the pack contains two of each letter and there are four different train car/color combinations, in addition to the caboose and engine.
Update: These are now available in my Etsy store: Engage and Grow.