The leather vest is very easy to make. It only requires cutting the material using the pattern and sewing (or gluing) the shoulder seams. If you use fabric, select something that won't fray, such as felt, or treat the edges with Fray Stop.
You can find the pattern here.
As you can see, the front of the vest won't close. You can make it close by modifying the front edges. First draw the desired shape in the pattern, fold the paper in half, and then cut the pattern. This way, the front parts will be identical.