You probably already know, but you can get a universal cat for a much more reasonable price than an OEM or direct-fit. If you're concerned about flow, you can get a high-flow cat, or one rated for a heavier vehicle (they seem to rate cats by vehicle weight). Assuming your car has 1 3/4" exhaust (which would need verification)
this list, for instance, should have something that fits.
We don't have emissions testing either, but my adult-onset asthma has made me appreciate working catalytic converters.