You're in luck. Bill Wilner, who runs MiataRoadster.com regularly has back issues for sale. Also, Phat Miata and the rest of us often end up with duplicate copies as we collect. What issues in particular are you looking for? Every issue has lots of NA content but if you want exclusively NA content look for the early issues and collect them all. If you can't read Japanese then they're all pretty much the same - just lots of different pretty pictures to give inspiration.