an old thread, woke up from the dead.
My Fontana faucets started leaking as mentioned in the beginning of this thread and here's how I fixed them. The insides valve portion of the cartridge is ceramic and crumbles after age (see the first picture, the left cartridge). Mine was from 2003.
<a href="http://s1266.photobucket.com/user/drapaki/media/IMG_6198_zpstyfm0hog.jpg.html" target="_blank"><img src="http://i1266.photobucket.com/albums/jj522/drapaki/IMG_6198_zpstyfm0hog.jpg" border="0" alt=" photo IMG_6198_zpstyfm0hog.jpg"/></a>
The manufacturer of the cartridges (at least currently) is a company named Donner. I found a supplier in South Carolina that sells them for about 22 deer each, 8 for shipping and they were to my door within a few days. https://www.fdsupply.com/
You'll need a cold and hot (they turn different). Here are the part numbers:
<a href="http://s1266.photobucket.com/user/drapaki/media/IMG_6207_zpsic7mlieh.png.html" target="_blank"><img src="http://i1266.photobucket.com/albums/jj522/drapaki/IMG_6207_zpsic7mlieh.png" border="0" alt=" photo IMG_6207_zpsic7mlieh.png"/></a>
and here's what they look like compared to the old one, which is in the middle.
<a href="http://s1266.photobucket.com/user/drapaki/media/IMG_6206_zpsjstqwbu4.jpg.html" target="_blank"><img src="http://i1266.photobucket.com/albums/jj522/drapaki/IMG_6206_zpsjstqwbu4.jpg" border="0" alt=" photo IMG_6206_zpsjstqwbu4.jpg"/></a>
This was half the price that Ferguson's plumbing quoted. half!