The best way to find breeders tends to be on-line. However, you can also look in pet store windows to see if anybody is advertising any there.

However if you log on to a popular search engine and then type in something along the lines of 'fancy mice breeders Missouri' it is likely to come back with many relevant results.

Also, have a look at the web page of the local fancy mice association club. They will more than likely have a list of fancy mice breeders. Failing that looking on classified websites for Missouri is one of the best ideas and there you should be able to find what you are looking for. If not then try placing a wanted ad in as many locations as possible and that should produce some results.