I also prefer not to spend money on buying hitai-ate (I bought Naruto's Shipudden version for $20, and I can't even use it for any of my cosplay!), so I've made a whole bunch myself. To make the metal part, I traced the shape on the official product onto craft foam, cut it out, and covered it in tin-foil tape. You can stick brads in for the studs (and paint or color them silver if you need to). You can engrave the symbol in with the tip of a pencil, pen, the non-brush end of a paintbrush, or whatever works for you. Once you make the fabric part you can attach it with fabric glue. Here's a photo with the one I made for my Itachi cosplay. It's the first I made, so it's a bit messy.
Judging by the date that this thread was posted, I'm too late to help you for the party. ^^; However, I hope that the method of making hitai-ate that I use can still be helpful to you sometime. I hope that your party was fantastic!