Just a quick search over at hammockforums.net got me this link:
Turns out the KAQs were designed to fit the Hennessey Hammocks. If you have the ability to sew, making a similar quilt out of 5oz. Apex would be a good project and not terribly difficult, I don't think. I haven't made on like this before though.
Since bulk is an issue for you, are you looking for a down or synthetic underquilt? Also, is your HH the kind you get in from underneath or with a side zipper? Because that would change the design of the UQ. Also, are you looking for a full length or something shorter fine?
If you haven't looked over at hammockforums, I would suggest you give them a google search because they have some great hammock specific information over there.