Here are a 1:1 (ideal for cosplay) and 1:5 papercraft patterns of the Captain America shield. You can find the files at [link]
including PDO and Blender files.
There are two 1:1 versions, one with the texture showed in the picture and another without texture so you can paint it.
The 1:1 versions are big papercrafts, you must cut the margins using the line guides in the corners, then join them to complete the pattern. Paste the model to bigger cardboard sheets to make it stronger.