It's kind of funny from my perspective, as I've used Ultiboard, where 3D shapes are extruded from 2D outlines. You're already done!...

Anyway...
I had to do a one of these recently, and didn't find a command for it. Didn't check scripts. Just drew a bunch of points (with a fine grid), approximating the shape. Took as long to draw as it likely would to find a better solution...
At least there's this: if you like arcs, you can draw arcs (in AD15+, I think?). Try CTRL+SPACE a few times while drawing.
Probably if you want anything more complex, you should do it with a real 3D tool, and get a file in VRML (along with a few others, can be imported and converted with a Pcb3DLib file), STEP (preferred) or SLDPRT (also new). And one I'm forgetting because I've never used it...
It's idiotic that 3D Extruded objects cannot be edited by vertices, as Regions can. Wonder if anyone's reported that in Bug Crunch...
The standard commercial method would simply be to lean over and ask your ME to cook it up real quick in SolidWorks or whatever. (I'm sure that's real helpful...)
Sure would be great if there were more converters for 3D formats, then again maybe I'm just not "in" and there are lots of good programs I don't know about...
Tim