Good question, I've searched for this stuff on the web to no avail. I finally picked up the magazine extension at a gunshow. It makes the shotgun look AWESOME! It is advertised as a +2 extension, but it actually ups the capacity of 2.75" shells from 4+1 to 7+1
i got my recoil reduction device from http://www.dnrsports.com/
i had ordered the mag extension but they were on back order and I have yet to follow up. The ordering experience with DNR was good.