So, I jumped on Google and started searching. I was very excited to have found a wonderful set of Superhero Alphabet Flashcards on TeachersPayTeachers! If you'd like to check them out yourself, click here. I printed and laminated two sets of the uppercase set. I kept one at school and I sent the other set home. He has been using them for almost a month now and he has gone from recognizing only 3 letters to recognizing 16 letters. It has been AMAZING! I am pretty sure he's going through a growth spurt because he can also recognize numbers 1-6 (numbers we have covered thus far) and he can also recognize all of his color sight words as well as the word "the".
Myself as well as the other support staff keep marveling at how much he has changed over the last year. It has been such an amazing transformation and he often brings tears to our eyes with his accomplishments.