As was stated, post up a video, because if you are still able to ride on it (which is how it sounds from your post), it should be repairable (as was stated).

If not, a quick eBay search resulted in a few $60 and $80 rear wheels. You could also contact Velomine or Retrogression to inquire about just a rear wheel (neither site has just the rear advertised, but it shouldnt be too difficult to acquire one).

If you have a co-op in your area they will most likely be able to assist you in finding a used wheel.