On the web, there is now an excellent site which sells all the major makeup brands directly. Operated by Steve Biggs, it has a wide selection, and lists some of the larger sizes, not just the little 1.5 oz bottles. I want to stress that before you start a painting with a new model, you should always test the product you are using first on that model. Try a small area, and wait several minutes, to see if there is any type of reaction. This is true even for supposedly safe make-up products.
Every person is different, with varying sensitivities.
I also make sure I am near a shower or hose to quickly wash someone off if they start to have a reaction. I've never had a problem, but I would love to hear from anyone who has. People breathe through their lungs, not their skin. Total coverage of a person's body with paint will not suffocate them. I'm speaking from personal experience here, so anyone who disagrees should send me some medical references or citations that demonstrate otherwise.