While the quad-core Transformer Prime has seen its fair share of negative accusations, it's still the tablet of the moment. In fact, it's so sought after that ASUS is having a hard time filling shipments and it's still out of stock nearly everywhere (sound familiar?).
If you've been waiting around for one of the major retailers to get a new shipment in, then make ready the credit card - the 64GB version in amethyst grey just became (re)available on Amazon. If 64 geebees is more than you want, though, they should be getting more of the 32GB variant back in stock on January 25th.
If you're picky about color and have your heart set on the champagne version, you have two options: take a chance and buy one from a third-party reseller, or wait until Amazon get some more units in stock.
Personally, I'd just go ahead and jump on the amethyst one - trust me, it's beautiful.
Transformer Prime at Amazon (Unfortunately, the dock is also sold out)