Got the battery in-hand and yeah, no faceplate.
More I think on filling the gaps around the battery, the simpler and simpler the tech I'm thinking of using since it's purely cosmetic.
I might cheap down even further with balsa or even insulation foam.
The foam would be easy to cut to shape, hit it with modge-podge, fiberglass gelcoat, or some other protectant so any hardener or paint doesn't dissolve the foam, 3-4 coats of lac or other hard coating, sand smooth, then prime and paint. Be a good afternoon project for an upcoming weekend. I really don't think this warrants anything as complex as fiberglass or 3d printing the more I look at the problem.
The original plate is oddly shaped, and might prove tough to replicate especially the spots they have that curve inwards. I'll probably just go with flat surfaces as I doubt many would notice the difference. I'm surprised -- though I shouldn't be -- that the original plate is glued on. Given the way it almost breaks when you try to remove it, I wouldn't be surprised if it's actually contact cement... which is probably what I'll use to apply my plate to the blank.
I think I'm going to leave the area around the power button uncovered. I can actually see the light without the faceplate and it's plastic over-button in place far better, which is one of my complaints about the stock battery. That blue light is impossible to see in daylight leaving you guessing if the battery is on or off.
I'll document best I can and post up my results here when I get around to doing this.
