Far as I know, items for a Mossberg 500 will work on the Maverick 88.
Only additions I have found terribly useful on a shot gun are as you mentioned, the side saddle. I love the speed feed stocks with the 4 round ammo storage as well. Not a huge fan of pistol grip in the rear, definitely not up front, but to each his own.
"People live too long, dogs don't live long enough" - FTF Member-