Cool mixers...
Too bad about the base of that chrome Mixmaster. UPS should definitely reimburse you for that. I had a similar thing happen a few years ago with a chrome Mixmaster I bought on eBay. The seller actually shipped the thing with the motor unit attached to the base!!! He gave me a complete refund and let me keep the mixer, so I found a white base on eBay and ended up with a complete mixer and money left over from the original purchase.
You should have a pretty easy time finding a base on eBay. If you've just got to have one right away, you might have to settle for one in some random color but I guess a functional frankenmixer would beat a non-functional mixer and the chrome head would look okay with just about any color. Of course, you could always paint it brown like the original if you really hated the color. If it were mine, I might be tempted to hold out for a nice chrome base. They're made of metal instead of plastic, so in addition to just looking really cool, they're also heavier and more stable.
You might also want to join the Yahoo group WACEM (We Actually Collect Electric Mixers). Somebody there might be able to help you out.