I am looking for a Christmas Thomas the tank Engline that will run on my North Star Express train track which I purchased from Sams (90041?).  I am a grandmother very new to trains and would like to get a holiday Thomas to add to my track.  I do not know what size will fit.  I think it may be "G".  Where do I find a Thomas and Emily that size?  Thanks a million.  Please respond ASAP.