I had not heard of the AEM filters - but if I ever find an instance where I want a K&N for something, I know what I will get instead. To be able to just wash the filter, dry it, and put it on would be great.
Concerning the Mirage and candidates for it's air filter, instead of trying to find a car filter that would fit, you might try to find a motorcycle filter that would fit. Motorcycles in the 1200cc range are rarely 3 cylinders, but there are a bunch that have just one intake/carb. And a filter that will feed a 1200cc motorcycle will feed a 1200cc car, no trouble.