My advice to you would be to find some for the standard mazda3 at discounttire or something like that (I generally just say its an mz3 because most stuff like this is the same and parts are much easier to find) You will overpay at the dealer, if they even have any.
The hub on the MS3 is 67.1, what you need to find out is how large the hub opening is on your wheels before you buy a set of rings so that you get the proper sizes.