Here's an easy way to make your own set of chest/collar armor and shoulder bells for under $20. You will need two STERILITE plastic garbage cans (available at Wal-Mart). Get one 13 gallon and one 8 gallon. Use the 13 gal trashcan to make the chest/collar armor as well as the abdomen and center diamond pieces. Use the 8 gal trashcan to make the shoulder bells. I actually used the 8 gal trashcan for my abdomen piece because the curvature fit me better. These garbage cans are oval shaped which gives the armor the proper curve for it to fit your torso. You will need a set of armor templates for tracing onto the cans as well as a pair of needlenose pliars, tin snips, and a hobby knife. By adjusting the position of the templates on the trashcan you can achieve the proper curve on both the x and y axis for the chest armor. The pictures should be pretty self explanatory. Trace the armor onto the garbage can. Cut the pieces apart using the tin snips. LEAVE ABOUT 1 INCH OF EXCESS PLASTIC AROUND THE TRACINGS OF EACH ARMOR PIECE. Next take your hobby knife and 'score' the plastic along the tracings of the armor. After you have done this you should be able to snap away the excess plastic using the needle nose pliars and you will be left with a nice clean edge around your armor. If you have any questions PM me and I will be glad to answer them. Oh and these garbage cans are really tough so you dont have to worry about your armor cracking.
I made a quick one like this for my son's school Halloween party. It was pretty easy to throw together. Made the 'cuffs' out of plastic cups and painted them. Rubies helmet from Target and I used the spare plastic to make the knee guards and attached them with velcro. He won "The best spaceman" award. He was pretty disappointed.