Pokeball USB Battery Holder. Fits Anker USB lipstick sized USB batteries.

https://www.amazon.com/Anker-PowerCore-Lipstick-Sized-Generation-High-Quality/dp/B005X1Y7I2/ref=sr_1_2?ie=UTF8&qid=1469043613&sr=8-2&keywords=anker+usb+battery

Should fit original PowerCores. Haven't tested on PowerCore+ but dimensions should work.

Print with supports or use half size and glue together. If printing HIPS you may not need supports at all when printing half size. You should finish with Bondo and spray paint. Cover in bondo, sand aggressively. Spray evenly, polish to a smooth finish.

Suggest using Bondo Spot and Glaze putty to create a smooth surface, and passes of sandpaper from 80 up to 2000.

Supplies:
Bondo #907
Rubber gloves
Masking tape
Rustoleum Apple Red Gloss
Rustoleum Gloss White
Rustoleum Flat Black
High fill spray primer
Superglue or Epoxy
160, 600, 1000, 2000 grit sandpaper.
Meguiar's M105, M205 compounds
Sponge compound applicators or dual action / rotary polisher if you are nuts
Clearcoat for the overachiever
A lot of patience for sanding

Tips for making this:

1. Make each half at a time. Cover with Bondo Spot and Glaze putty #907. Smooth using rubber gloved fingers. Wait for it to dry, about 15 minutes.
2. Sand with 160, then 600 grit.
3. Apply more 907 where you had low spots and missed areas. Wait to dry.
4. Sand with 160, then 600 grit again. Repeat if necessary. You should have a very smooth ball at this point. Clean sanded areas off with dry cloth.
5. Shoot with spray primer. Sand with 1000 grit.
6. Shoot each half with gloss spray paint. I used Rustoleum Gloss Apple Red and Gloss White. Allow to dry 24 hours.
7. Wet sand with 1000 grit, then 2000 grit. You should have a non glossy appearance. It should look kinda dull. Spray paint again if you had to take out a lot of paint in sanding due to runs, etc. Repeat sanding until smooth (but still dull after sanding). Clean sanded areas off with dry cloth.
8. Sand interior channel where the USB battery goes. Check fitment.
9. Glue together using superglue or jbweld / loctite epoxy.
10. Apply more spot putty and sand to erase the edges.
11. Mask red and white areas with masking tape. Shoot flat black spray paint. Sand.
12. Remove masking tape. If overspray, curse loudly.
13. Using Meguiar's M105 cutting compound and a sponge applicator, polish.
14. Using Meguiar's M205 polishing compound and sponge, polish. The thing should be ridiculously shiny.
15. If you are an overachiever, apply clear coat. Sand. Polish.

Edit:
Added a nice render :)
Added some WIP pictures of Bondo covered half.
I'll add more pictures as my paint finishes drying.