Scot Steele , Apr 10, 2007; 09:22 p.m.
I've bought cheap mannequins for art projects at the major online auction site. You can buy a head (with neck) for about $15. Full bodies are far more expensive, but probably not necessary for your purpose. You can also get a cheap wig for checking what a bit of back-light looks like with any given light set-up. Real wigs are pricey, but costume wigs are $10 bucks or a bit more, and probably good enough.
Best, Scot Steele