I am helping my daughter make a "Chell" costume and in doing so found a great way to pull together the Long Fall boots for very little time or money.
The boot effect itself is a sock that is on the market on a few sights (around $12):
The spring part is what we will be building..Parts will run you around $7
You will need a couple foam sheets:
Black for the "blades" http://www.amazon.com/Foamies-Inch-x18-Foam-Sheet/dp/B0018N0F44
White for the "brackets" http://www.amazon.com/Foam-Sheet-12-X18-2mm-White/dp/B0018N5TJ0/ref=sr_1_cc_1?s=aps&ie=UTF8&qid=1349752937&sr=1-1-catcorr&keywords=2mm+white+foam+sheet
You can find these locally at most arts and craft stores (like Michaels or Joann)
The two straps with clips are actually "Cat collars" that I purchased in the pet department at the "Dollar Tree" for $1 each. They are adjustable and work great.
You will need a couple feet of fishing line and a sewing needed as well.
A utility knife
A board or book to help cut straight lines
I used hot glue to hold things together.
Cut a small rectangle for the main support of the boot blade. The size may vary depending on how big your lower leg is but this one was about 3" across.
Place the collar strap in the center of the cut foam sheet. Now you will only hot glue the lower white part and fold the foam over the collar so it can still slide freely for future adjustment. You are basically making a belt loop.
Cut the blades from the foam sheet I made these about 11" ...basically cut a two inch piece across the long end of your foam sheet. I used a spare wood block to keep things straight and from moving around.
Hot glue the black blade to the white loop as seen in the photo above.
Using fishing wire and a needle you want to create a little bend about halfway down the blade. I created a looped square from about 1" off the base to a little shy of halfway up the blade and pulled the lower part up.
Step 6 adjust the strap to your leg and snap over the sock and you are done!