I've got some 3D models for bucks for those who would like to vacuum form one. It is based on dimensions Mike posted at the RPF and tracings of auction listings. I also have an original set of shells to compare it to, and I think it comes out pretty damned close.
(This is two bucks stacked on top of each other—thicker than the final cut-down size of the medkit).
You'll want to cut out this profile in four layers of 10mm thickness and one layer of 6mm. That's for each side/half.medkit profile.dxf
You'll want some 50mm x 10mm diam. dowel pins through those holes to glue the layers together in proper registration.
Then use a 5mm radius bearing bit to mill the edges. Just make sure to radius different sides of each half.
Then comes the hard part of making everything else. =\ I can't help with that—er, well, at least not yet!