What type of screens do I need for this crank case window

What you are looking for is called a Combination Storm/Screen Window, and most hardware stores can order exactly what you want or you can pick through the selection at The Home Depot: Window Screens is a wide variety of combination storm window/screens to pick from.

The third picture tells the story. Working from the outside, disengage the knife latches on the right side (the picture shows one near the top but there are usually two), then slide the screen to the left to clear the the frame from the right-side channel. Then pull down, out of the upper channel. The frames are aluminum and sometimes get stuck due to oxidation, so spraying the channels liberally with WD-40 or similar penetrant may ease removal. Be careful not to bend the frame, but be prepared to replace the unit. A good mom-and-pop local hardware store should be able to custom fabricate a replacement. They make plastic clips that snap over the frame that will serve the same function as the knife latches, as not all shops know how to install them.