I just got a 92 mazda mx3 and the interior is pretty beat up, is there any other cars that use the same interior or sites that have some, or anyone selling interior parts for it?

 

You will likely need to hit the junkyards to find a new interior. Most any seat will fit if the bolt pattern is the same for the seat tracks.

 

If I am not mistaken the MX 3 is based on the 323 and Protege. So is the Mercury Capri convertible. That should help finding decent seats. Make sure you can take them back if you cannot make the seats fit.

A good cleaning and an application of paint for plastics can freshen up a car quite well. I cleaned the interiors of 2 old cars with a Bissel carpet and upholstery cleaner.

 

The worst of the interior is the armrest, rear seats and trunk plastic

 

If the armrest and the plastic in the trunk are only scuffed you may paint them with a rattle can of duplicolor for plastic.

In fact took for videos on how to fix interiors, broken plastic etc. The rear seat is probably dedicated for your model.