I noticed one with 5 extra magazines and box sold for over $900 yesterday on GB (Item 874516942). A couple of the extra magazines were in sealed boxes, marked 3906/909, and S&W p/n 190580000. Someone else would have to confirm that these actually work correctly.

If I were going to shoot it, I would take one for $450 used and with no box anytime.

Assuming that those magazines are correct for the gun, they can be found for a decent price online, and since they are under 10 rounds, even on ebay, !