Wally World sells those cheap UniFlame grills. They did sell one (and maybe still do, but I haven't looked lately) that has 24-1/2" grates that are hinged. The top measures 26-1/4" inside the lip. These might provide your grate and a domed top.
OK Joe Longhorn & Original Ok Joe Vertical Roasting Oven hybrid, Char Griller Akorn, Falcon MK V gaseous grill