Tipped off by an article in a recent Toy & Hobby magazine, mentioning that Hasbro had licensed JayJays to release t-shirts for the Fall of Cybertron game, I just had a look on their site and found two.

Decepticon - purple
Autobot - navy

They are both included in the current sale of "two for $30", or are $20 each.

Also noted is the remaining few items on their online store from the last assortment are being heavily discounted. $5 for the (XS & XXS) T-shirts, $15 for the (XS) hoodie. If any of the last batch are in stores, they could also be discounted.