Front Storage Hatch

[Fishbone lures]

Looking to get some help on my front storage hatch. I have a 1976 23 SF inboard which was nicely restored. When the restoration was done the front storage hatch was covered over. I want to cut the deck and open that hatch back up to be able to use it for storage of life jackets and misc things how ever i'm not sure what to do for a hatch cover. Ideally id like to keep it as flush as possible. Does anyone have any exigence making a replacement hatch base off of the specifications for this box? I would go with an after market cover but I need it to be water proof and as flush as it can be. Any help would be great.