I was trying to get one this morning too, but was a little too late. I am not sure why you couldn't find it, but Memory Express definitely had it on their website, and they still do (out of stock now, obviously). The guy I talked to said I missed it by about 2 minutes! Oh well, looks like I'll have to let the dust settle and grab one from the next batch.
When I called staples, the guy indicated that according to the system, the transformer will be an online item only, and that they should be getting another batch "in a couple of days". Not sure I believe that one!
I have an account at MemExpr, so I will probably just put my name on the waiting list and they will hold one from the next batch for me. I noticed that the 32G model is available for pre-order too.