I believe a sharpie is not the correct color of black. A vacuum chamber can be useful for dying things, especially if you have a dual chamber setup where you can first evacuate the bone, thenopen a valve, letting the dye enter the chamber, and then apply pressure, driving the dye even deeper. The most expensive part of this setup is the vacuum pump. Vacuum bags/ clamps are cool, useful for things like, say, laminating neck blanks. Bar clamps do not even come close to the quality of even pressure achieved in a vacuum bag. If you have a vacuum pump, designing a chamber is not difficult. Stabilizing wood uses this same technique, of impregnation in a vacuum chamber. (wow, that sounds bad!....)
Of course, it is easiest to just buy something that will work, unless your artistic side tells you that you need to make it yourself because what you want is not available.