MicroDIMMs. Requires those awful, awful Hirose connectors, though... and they're not widely available (by which I mean "sold on eBay").

Or a proprietary (by which I mean "part of the standard but not used anywhere else") module setup, with the same drawbacks...

I was really thinking it would only fit the Type III cards anyways. With the Type IIs, it sounds like you could 'cheat' by having a sheet of plastic over a shell cutout... but those size requirements are a bit, well, oy. You've got a point there. I didn't realize the outlines were that close.