According to the parts lists I had printed some time ago from the Four Winns site for my 2002 268, the Bomar hatch is Four Winns P# 060-1316, Bomar P# N1139-MOPX-KWHT. According to the parts list, this hatch was used from "2000 to present". A google search shows that Bomar is a part of Pompanette Companies, whose website lists the "1139" hatch (and many others). The following link to their chart shows the "1139" hatch has a hatch opening size of 19 3/16 inches. I understand that the letter "P" in the part number indicates plastic frame, and the "KWHT" means white frame.
https://pompanette.com/product-series/d ... ies/#sizesI'm not sure this hatch is still available, but you could call their product support to see. Hope this helps.