Correct. To my knowledge Maxum used Bomar hatches on all of their models. Have you checked this site out yet?
http://www.pompanette.com/bomar
Bomar is a division of Pompanette LLC. You should find a large selection of parts for various models. Try giving their Customer Support a call. For that matter, you should be able to have a local Searay dealer do a parts lookup for you and see if they are still in stock. They are used on Maxum, Bayliner and Maxum and I'm sure a variety of other models, so I would be surprised if they couldn't get them. Finally, try calling Maxum TEch Support. There is a sticky thread with contact links in it. you might need to scroll down to find the most recent contact update.
I hope that helps.