Seen them at cabelas and wholesale. As well a couple other shops in Edmonton. You can probably order one as well since most shops are benelli dealers.
I don't know if you can order the MR1 stock but I put a Supernova adjustable on my MR1. The trigger guard flares out more on the MR1 than the Supernova. Just took a little work with the dremel tool to inlet the pistol grip to accept the MR1 trigger guard. It's not visible from the exterior of the grip.



























