I saw XXL. Anything bigger than that is bigger than a nerd they can accommodate. Haha. I was once 365lbs bro, I feel your pain. I have been there... I remember. 100+lbs later, well... life is better.
I wore the same one yesterday. I actually picked it up at Kohl's at the beginning of the year.They always have great t-shirts and they're always like $9.99.Plus i get the 30% off cards in the mail all the time so I end up paying only $6.99 for the t-shirts.
I'd be half-tempted to buy one, sew up all the openings and then stuff it to make a t-shirt-shaped Transformers cushion. Would that be cool or weird? At least then you could kinda enjoy useful Transformers t-shirts even if you didn't wear them.