If your sure it is " toast " .... then why not take it apart and see what is causing the binding ... some of the best times of my life have been taking apart machines which I could justify not having to put back together ...

Most electric motors are very simple things... if you are careful taking it apart you very well might just replace a bushing ( a bearing made of porous solid material as compared to a roller bearing ).

Or, if you look at it and the windings look ok,,,like not charred...then you might seek out an electrical motor repare place..... go as commercial as you can.. a big place that handles lots of motors.... take it to a couple and get their advise... they will be able to say something after using a volt/ohm meter on it... as to the condition of the windings... and it may be a simple deal to replace the bushing....

It is also very possible you can convert to other electric fans...

Check your local library for books on repairing electric motors before you start... and take pics for the FAQ pages.... Greg