Train Spells Tomas

Tomas' cousin Holly made this for him when he was born and it has sat nicely on a bookshelf ever since. Within the last month or so though he has become really interested in it and likes to bring it downstairs with him in the morning and then bring it back upstairs at night when it's time for bed. Pictured is the caboose and the letters O, S, A, and T. I'm on the lookout for M.