If you need to make a prop or accessory for your costume and the item needs leather, consider this alternative shared by Andy and Nat Dempsey with The Replica Prop Forum (RPF) Facebook page. Instead of using the costly material, he turned craft foam into a leather like substance. To accomplish this, he put a sheet of crinkled aluminum foil over the craft foam, turned an iron to its hottest setting, and ironed over the craft foam. Having the foil between the iron and the craft foam prevents melting and gives the craft foam a convincing leather texture. That texture will really pop with light washes of paint.
To add faux stitching around the edges, a commenter suggested using the tip of a flathead screw driver to leave the marks.