if all else fails, flesh colored bra. Put skin colored makeup on it if you must, but people will care less about seeing your bra than you think.
Sew a bra into the front. Get either breast cups or cut the part of the bra that will be visible off, and sew/glue/whatever the front of the bra where it will need to be to give you proper support. I recommend also using fashion tape to hold that in place on your body on both sides and possibly reinforcing the neck. Those things should all be relatively simple and not require a great amount of skill, just a some minor catch stitching should do the trick.
Best of luck