Mass Effect Trilogy on PS3 - where can I purchase it?

Hi
I've been hunting around for the PlayStation 3 version of the Mass Effect Trilogy, which seems to be out of stock in most of the online stores I have looked at, and those that do have it in stock are pricing it too high. Also it doesn't seem that the supermarkets or Blockbusters are getting stock in either. Is there only a limited run of the Trilogy getting released, or is there another reason for the lack of stock? Many thanks