What about using 2 pieces of sculpey and actual sized models of the
batteries and circuit, spraying them with some type of mold release and mashing those together trapping the models within. After it bakes, take out the models and replace them with the real components. You'd then have to join both halves with screws or magnets, of course, but it'd be pretty darn kewl!
Note: I'm not saying I've done this or even if it will work, BTW. Just hopeful wishing! I guess it all comes down to what kind of mold release (if any) would work.