A cheap way to make a body form yourself is the trash bag and duct tape method.
Put on an old t-shirt that you won't mind getting cut, and probably some old pants just for good measure. Have scissors at the ready in case something goes wrong. Also, you will be standing in one place for the whole process. Do not lock your knees. It's also a good idea to do this in an air conditioned room, because plastic and duct tape doesn't ventilate very well.
Get a large trash bag and tear hole in the bottom for your head and then a hole for each of your arms. Your going to want one that covers you below the belt when you put it on over you. Then, have a friend start wrapping you in duct tape everywhere on your torso that's covered by the bag. I'm a big guy and mine was done with less than two rolls. Have them wrap snug, but not too tight. I will tell you that by the time the wrap nears completion your breathing may feel slightly labored, but you should be fine if your friend is efficient in finishing up and you stay relaxed.
Once the wrap is completed, your friend will take the scissors and cut the tape and trash back down your back until you're free from it. After it's off of you, reseal the cut with more duct tape.
I recommend stuffing it with newspaper until you can tape up the neck and arm holes. You can finish stuffing with newspaper if you wish, but overtime, newspaper will not keep it's shape as well foam packing peanuts or, if you really want to get fancy, expanding foam. Obviously, if you use something like expanding foam, be aware of all product warnings and test it out to make sure it will meet your needs.
I hope this will help you.