I doubt the people here has a Mannequin, less so having 4!
I have only Size 10 Mannequin (currently using it, so can't lend), and a very small one for drawing/modelling lights.
You may want to try borrowing LaSalle or Raffles Design school. Buying 4 might be out of question cos these costs a lot of money.
http://www.lasallesia.edu.sg/secondary.html
http://www.raffles-design-institute.edu.sg/
Good luck!