Not the GP, but I was able to pick up a new 4gb model from the Acer online store a few weeks ago (the Canadian store - I don't think Acer is selling it new in the US anymore).
If you're unable to find one I believe the new Dell Chromebook 11 is fairly similar.
For developers, installing Crouton turns the Chromebook into a fantastic portable machine. My Acer c720 has been able to handle everything I've thrown at it, and generally lasts a full day (10-12 hours) between charges.
I don't see the problem. Google is letting people pay to beta test their product. They aren't forcing anyone to buy anything nor are they marketing it as a finished product.