There are many topics explaning what you can do with foamies, and are quiet a few tutorials on how you can make these things with foamies. Hell Ive made some shoulder bells, a energy back pack, shurikan and gaunts out of foamies.
Basically they are these foam sheets, not very thick, some come with sticky backing, some dont. Some come in rolls, and others come in well sheets. They all come in different sizes and colors and are VERY cheap. Foamies are very easy to work with, and I use them a lot for some of my armor pieces. You could get them at your local hobby store. If you dont know were to find them just ask sombody and they could point you out to them. They are also called "Fun Foam".
Take a look around here, you can find a whole bunch of stuff on here about foamies
Kish Kish