[header] How to make a bam bam costume [title] Buy a half a yard (0. [step] Felt from a bolt at the craft store works great for this project because it doesn't fray. You can also dig in your closet for an old orange or brown t-shirt or sweatshirt. 
[title] Measure the circumference of the costume wearer's waist. [step] Buy a half-inch width of elastic that will cover this width.