I used to share a po box with my friend in nevada, that subscription went for a really long time as well, but I let him keep all the free mags that I had there
If your not able to locate any of the magazines that have it - the best thing you can do is post in the coupon/trade thread that you are looking for it and offer up something for trade (stamps, other coupons, etc.). Most people do not want to give away FREE product coupons because they can trade them for things they want/need.