Lifesize Body Forms Its fairly cheap, less than $20 for a sturdy, water resistant and reusable form. Outside friendly. Just add your favorite costume! Use PVC frames and simply add empty 2 liter bottles for leg filler. Incidentally, the necks of the bottles fit 1/2" PVC pipe perfectly. Just use a 7/8" bit to drill a hole in the bottom of the bottle.
source: https://www.pinterest.com/pin/396105729699858642/