I do not know of any realtors in OC that have registered group rental properties, but they do exist. You can google 'Ocean City NJ group rentals' and find some, including at shoresummerrentals.com, that specify that they will rent to groups; you can also look on http://www.vrbo.com for properties that specify that they accept groups. If all else fails, come to town and drive around In a grid, street by street, in the 6th to 14th St area, and look for signs on some of the large, older buildings.
Hope this helps,
Monihan Realty Inc,