If you build this out of foam, this actually shouldn't be too hard of a belt to build your own template for, and I am saying that having read and understood that you are not that great at drawing.
Measure around the part of your body where the belt will rest (wherever between your waist or hips that that is), adding a half inch to allow breathing and movement space. That's the length of your template.
Thankfully that belt's top and bottom edges are straight lines, and the look to be about 2 or 2.5 inches apart. That's the width of your template.
Get a large piece of paper, poster sized or like that. Take a yard stick or some other long straightedge and draw a straight line to your length measurement. Next take the yard stick or the ruler and line it up perpendicular to the edge of that line, and make a tick mark 2 or 2.5 inches from your first line. Repeat that along the first line at regular intervals (every 3-5 inches) until you reach the end of your first line. Now use that straightedge to connect the tick marks, and you will have the top and bottom of the belt.
Next you are going to draw half the belt buckle on one end of your belt. Start at the top edge, go a little bit in, and draw the ear. From there, you can follow the lines from your picture to complete half a belt buckle. You will have to experiment a bit here, but the design of the belt buckle is nearly all straight lines, so drawing ability won't hurt you much here as long as you use a straightedge.
Once you finished, cut it out and trace it onto a sheet of foam, flipping it over the middle of the belt buckle to get one long piece. If you don't have a long enough piece of foam, trace the two halves separately and cement them together down the front of the buckle (leave the back end unglued so that you can put whatever type of fastener you want there). The rest of the design (the zig zag lines) can be created with a a blade or a rotary tool used to score the lines into the foam.
I hope that gives you an idea. If you are set on using an existing pattern, you could check out TheFoamCave on Etsy to see if there is anything you can use there. I know there is a Batgirl template, but I don't think it is this one.
Good luck!
