My original idea for the APRS + voice gadget was a snap-in battery pack replacement holding the circuit boards and connected to an external battery pack. A trio of dead Wouxun radios, plus the ready availability of 18650 lithium cells, suggested putting two cells in the backpack, along with the circuitry, and skipping the external pack.
Here’s the base of a Baofeng BL-5 pack overlaid with a 1 mm grid:
The grid is parallel to the case body and centered left-to-right, with a Y grid line set at the front face of the pack, where it’s also flush with the lid surface. You can read off the coordinates of all the points, feed them into your CAD model, and maybe, with a bit of care, get something 3D-print-able.
Haven’t used it yet, but it’s bound to come in handy at some point.
The Smell of Molten Projects in the Morning 
If the detail is relatively flat, I’ve been known to stick things on the scanner, import the scan into Inkscape/Gimp, vectorize it (Gimp calls these “paths”), then export the outline as DXF. It’s a bunch quicker and more accurate than reading a coarse grid. All the flatbed scanners I’ve ever used have been very accurate on scale, and the image resolution settings automatically get carried across.
It’s flat-ish, but the contrast seems dodgy and the mold relief on those pins requires windage. I’ll try the scan-to-vector trick the next time I need an extrusion-like widget, though, ’cause the DIY coordinate thing is definitely getting old.