OK its super easy to DIY...I just made one for my Giro Remedy and my friend, LiveLife, made one for his helmet as well and they fit great.

Materials:
- sheet of 1/300th of an inch plastic
- contruction paper
- pencil
- painters tape
- grease pencil/marker
- scissors
- phillips head screw driver
- sandpaper/griptape
- velcro

Process:
1. Go to your local plastics distributor and purchase a sheet of 1/300ths of an inch plastic, cost is about $11-$12 for a 21" x 51" sheet.
2. Take your helmet and tape a piece of construction paper to the face opening area (or just half and flip the pattern to make the full pattern).
3. Trace the face opening through the neck opening. pencil in area for tabs to attach visor to helmet.
4. Cut it out leaving 1/4 inch around the shape that was traced to allow for overlap onto the helmet.
5. Transfer pattern onto plastic using a marker or grease pencil..(i used grease pencil due to the fact that it wipes off as marker does not)
6. Cut out with scissors. Once cut out attach to helmet and trim areas as needed.
7. Use marker/grease pencil to mark spots for screws to affix facesheild. Use a phillips head screwdriver to bore a hole through the plastic where screws will be.
9. Take sandpaper/scrap griptape to sand edges of faceshield.
10. Install facesheild to helmet and apply small strips of velcro around bottom edge to keep visor in line with helmet and from flipping up while speedskating.

Im sure this was already written up somewhere on here but I did all of this in less then an hour (including trying to apply mirror tint, no joy) and now I have a ridiculously awesome faceshield that will keep my eyes from watering up and bugs and debris from getting in my face while DH skating.

Hope you guys enjoy.