If you are familier with a filing cabinet, look at the file hardware that is used to hold the hanging files. I used the part the file hangs on. It is easy to bend and is the right width for the grips. Look at the photo, the little metal bar on the left of the photo is the bar I use. Most office supply stores should have these. If you buy a cheap set you can get about 6 gaurds from the 2 pieces.
Good Luck,
Brian
This link is to what I use. It is just for reference and not a sales pitch. You can find these at a vendor near you.