If not, you will have to make your own. During the construction of the slipcovers, you will have to pin the material on the chair to make sure it fits. You will have to make your own judgment on how snug the material fits. Always choose close knitted fabrics for slipcovers, making sure the material is heavy and durable for the chair. This is a necessity if you have children and pets.
Leather is a great cover but requires upkeep to keep the leather looking new.
Velveteen is pretty, but not practical, since it wears faster than other materials. To start, in your mind, divide up the chair into sections as you are looking at it, he cushions being one section each and so on. The next step is to figure out how much fabric you will need. Try using a cloth measuring tape and running it over the sections and measure for lengths and widths. The lengths are what you will need to add up for purchasing material.