While you've got it apart, measure the spindle and/or look for size markings -- often a number and letter(s) like "3S" or "3NN". If you're lucky, it's one of the remaining available sizes, or close enough. For about ten bucks, you can order a replacement and have things put back together before your LBS would have a chance to take a look at it.

If you measure the spindle, there are a few measurements you'll need:
* Overall length, not counting the threaded studs.
* Length of each side independently, from the lip of the bearing race to the end. Again, not counting the threaded studs.
* Length of the center section between bearing races.

So, for example, a 3S spindle is 124.5 mm overall and slightly asymmetric, 35/52/37.5 (left/center/right).