Of course, any other suggestions are welcome. I've been trying to avoid a DIY project, but I'm also open to any good ideas.
Stop messing around and get the real deal. http://www.pelican-case.com/#
Lifetime warranty, buoyancy ratings, pressure release valves, done. My old laptop case got cracked by a tank in Iraq but it saved the laptop and got replaced for free when I got back. That's protection. I don't screw around when it comes to my gear and it sounds like you don't either.
I would sort by size and match to the internal dimensions of the case providing for added foam if you wish. Pick and Pluck foam will let you fit your headphones to the case. I'll have a look since I have a pair of D7000s next to me.