In all the years I've been making movies finding mannequins
has elluded me. At least cheap/used ones. You can buy them
new, but they are expensive. I've occationally found one in a
thrift store.
However, for stunt use you might be better off building a stunt
dummy. I have built several - all caller "Bob the dead guy"
First is the skeleton: I use 1X2 and various sizes of wood (and
sometimes steel) dowels. Steel is heavy but more durable - wood
is sturdy, lighter and when it breaks it’s easy to fix.
I build everything except hands and the head. I use leather strips
appx. 1.5in X 3.5in for the joints (wrist, shoulders, elbows, hips,
knees, ankles) that are either screwed or riveted to the “bones”. If
you do this right, the joints will only bend in the correct direction.
In some cases I’ll wrap each bone with gaffers tape.
Then I cover the bones with various densities of foam, from harder
around the chest to softer for the arms and legs. I use Super 77
adhesive to attach it and an electric carving knife to sculpt the foam
to the shape I like. I also lay in my blood tubing at this time - using
Y and T joints I make sure I have exit points at the wrists, ankles and
neck. I even have exit points at the chest and back to I can do “bullet” hits.
You can buy hands at many novelty shops.
For the head I build a shoulder area that can be changed out depending
in what effect I need. I can put a cut neck for a severed head effect.
With some experimentation you can build a working, realistic dummy
for movies and haunted houses.