I didn't find a pattern quite like I was looking for, so I made one up. The pattern below shows the size and colors to use-I used black but many of the classic batman costumes use a deep blue instead of black.
Here are some quick instructions-I didn't take photographs while sewing it up, but it should be fairly straightforward...I hope.
1. Cut fabric pieces. I've allowed for a 3/8 " hem, but you could use a smaller hem if you like, there aren't many places where it would create a problem.
2. Take the gray piece, and press a 3/8" hem along one of the 15" sides. Pin it to one of the black top pieces so the bottom and sides line up, and the pressed hem is folded inward and is at the top. Clear as mud? Good. Topstitch the gray along the pressed hem with gray thread, and baste the sides together closer to the edge than 3/8". (If you intend to sew the logo on rather than fusing it in place, attach the logo now. See step 8.)
3. Pin the black top pieces right sides together so the gray piece is on the inside. Sew around the sides and top, leaving the bottom open. At the top, narrow your hem to form a point. Trim and clip seams to make turning it inside out easier. Turn it inside out and press. Topstitch with black thread close to the edges.
4. Sew the two sash pieces together to create a (nearly) 90" long piece. Press seam open. Fold the sash in half so it is 90" long and 4" high, with the open edge on the outside. Sew one short edge, and the long edge of the sash, then turn inside out through the open end of the sash. Fold in the raw edges of the open end of the sash and sew closed. Press.
5. Hem two short sides and one long side of the apron skirt. Gather the top of the skirt so it is 15 " wide.
6. Fold in the raw edges of the top. Press. Insert gathered edge of skirt about 3/8", adjusting gather to fit if needed. Pin in place, then topstitch over all layers to attach skirt to top. (Don't worry if the front seam is perfect, you'll be covering it with the sash.
7. Pin center of sash to apron, so lower edge of sash is slightly below where the skirt meets the top. Topstitch in place using black thread, and add extra seams to form the "utility belt" If you wish the lines to be darker than mine are, you could use a zigzag or satin seam.
8. I'll leave replicating the logo to you, I just found an image to use as a template and layered the black, yellow and black together with strong fuseable interfacing, then fused it to the apron. I considered topstitching the logo to the apron, but that really should have been done when the gray was attached so the seam didn't show on the back. I also decided I liked the clean look the interfacing gave.
*tip-when using double sided fuseable interfacing, it is a lot easier to cut the shape after fusing a slightly larger piece of interfacing to the fabric. Fuse the interfacing to the wrong side of the fabric, and keep the paper on while cutting the shape. Remove the paper just before attaching it to the next layer. If you cut the fabric first, you'll get a mess when the iron touches the exposed interfacing, and if you cut the interfacing first, I've found you don't get as clean of a cut. Start with the biggest shape first and layer up, then fuse the finished logo to the apron.
9. To finish the top you have a few options. You can create strips of a contrasting color (gray or yellow will help the "ears" stand out) and use D rings to create an adjustable neck loop. You can also use a piece of elastic as I did here, and just sew it to each tip, creating the proper height of neck loop. This didn't work out so well though-it fit me fine but my sister is a bit shorter and it would have worked better to attach a hook and loop to the tips. That would have made it fit her torso better.
Hope you have fun with this! I'd love to see any you make-especially if you go for other superheroes!