I wanted a 14-tooth front sprocket for my XT-250 instead of the stock 15-tooth sprocket, which is just a tad too tall for such a small engine. I searched everywhere and finally found a place that will sell you just about any sprocket you need. The 14-tooth sprocket was only about $20.
Here are the details:
Advanced Precision Pro, dba Superior Racing Sprockets
PO Box 2179
87906 Bill Creek Lane
Bandon, Oregon 97411
Local 541-347-7262
Toll Free: 888-347-7262
Fax: 541-347-5269