For anyone that's interested, there's a MAD Super Max choke for sale on ebay that fits a Mossberg 835. It's listed as a regular MAD Max choke but you can tell from the packaging in the picture and description that it's actually a Super Max. The description claims the choke is .695, which matches the constriction of the Super Max.
http://www.ebay.com/itm/300646977460?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649