I was asked where to get a model head like that shown in the e-book The Life in Figure Drawing. It turns out there is a new product made by a sculptor called the Facial Feature Model.
Go to Blick Art Materials and search for "Facial Feature Model" in the search box. It comes in 5 ethnic varieties: Europe/England, Asia/China, Africa/Cameroon, Asia/India and South America/Columbia.
Here are some related products.
Plaster Casting- Human Male Torso Model
Plaster Human Skull Model (Life Size)
Plaster Anatomical Casting- Human Foot
Plaster Anatomical Casting- Closed (Gripping) Hand
Also useful might be makeup manikin heads:Diane Manikin Head * Alicia * 16, or Celebrity Mr. Sam Manikin 19
A manikin for anatomical studies is Female Anatomy Figure: Version 1.
And, if you are interested there are the regular artist's manikins: Art Alternatives 12 inch Male Manikin, plus this hand manikin: Wooden Hand Manikin- Adult Right Hand and these inexpensive 4-1/2 Inch Wood Artists Manikins.
Wooden Human Mini Mannequin (Unisex) 12 Inches Tall
Art S. Buck Anatomical Manikin MaleMagnetic
Wood Manikin (7-3/4 Inches Tall)
There is also this manikin specifically for drawing Manga or Anime: Obitsu Manga & Anime Figure- Female.
Obitsu Manga & Anime Manikin and Figure- Female (Large Bust).
Obitsu Male Anime & Manga Figure and Manikin
Here are a couple of posable action figures which would serve the purpose:
Side Show Collectibles Art S. Buck Artist's Model male
Side Show Collectibles Art S. Buck Artist's Model female