After experiencing the same frustrations as most of you I asked a trusted mechanic-(several times he could have ripped myself off and several of my close friends via brake, AC, Rim info.) but has not= trusted.
Mechanic stated: measure your current 12" Festiva rims top right hole to bottom right hole-(rim bolt holes). And then top right hole diagonally across to the bottom left hole. Remember these measurements in inches or millimeters and measure any 13" rims that match these. These rims will work on our 12" hubs.
I'll be doing this soon as the only tires I can now find are : Yokohamas #:Y372; 165/70SR/12 at $51.00 each.

Found these at tirerack.com.
I believe there might be another forum on this at : festiva.com. Under repairs.
E95