Transformers Generations Combiner Wars Devastator, then Amazon might have you covered. The retail site has a pre-order listing for the 18" toy that combines from six Voyager sized Constructicons. The release date is currently set for August 1, 2015 for a price of $150 with free shipping. and you can find a picture review here. As for its retail store release, so far this is all we have but I assume at some point it might hit Walmart, Target, etc in the states at least.
You can pre-order Devastator by clicking here.