If you have a buddy that has a choke that will fit your gun that is your best bet to trying different chokes. Myself I shoot a Jellyhead attached to a Benelli SBEII.
I also shoot either the Win. Extended Range, Hevi-Shot Magnum Blend, or Nitro H518. The Nitro's are my favorite but at $10 each can get pricey. They still shot some of the best patterns out of my gun. The new XR from Winchester loaded in #6 shot a very good pattern as well.
I think your best bet for the money is the Primos Jellyhead .690. Unless things have changed I think you can get one for about $50. If you want to spend some money get an Indian Creek. I've also heard some good stuff about a new company called Wildside Armory.
Be aware. These choke and shell combos are best at 30-40 yards. When you get inside that range you are basically shooting something the size of a baseball (10 yd) or softball (20yds) at something the size of your fist.
If you are set on 4's (I prefer 5's or a Hevi-shot 6 or 7) you might want to op for just a plain 'ole extra full turkey choke from Mossberg. The larger the shot the less constriction you want.
In the end I say go with a Jellyhead. Mossberg's are overbored so I would avoid anything that constricts too much. Pattern it at 20 and 30 yards. Using #4's gives you good knock down but limits range.