Ford has the blocker rings, Do you mean the entire syncro hub assembly? If so you will have to go to Mazda for those. There is another thread with the Mazda part numbers in it that was started by Les Borda. Here are the numbers he listed.
1 - 2 synchro ... S50417260C
3 - 4 synchro ... S50517260D
5 - R synchro ... S50617260A
These will fit all of the 89 - 95 SC cars. Be forewarned, they are expensive. List price in Canada is about $275 each for the 1-2 and 3-4 pieces, and $185 for the 5-reverse.