Yes, you can make your own, using 1/8" plywood, a jigsaw, a drill, aluminum screening, hot glue, and some h-shaped -- NOT H -- aluminum (this is found at hardware stores in 3ft lengths). Please use HOT glue, not the ones that melt at lower temps.
Make a paper pattern of the window, trim off about 1/4" all around, and cut off about 4" all along the bottom (discard). Transfer to a piece of cardboard for a sturdier pattern. Fit the cardboard pattern into the top and side grooves of the window to check fit.
Make another cardboard copy, and mark a 2" border all around with curves at the 2 upper corners. Cut off the 2" border.
Place the larger cardboard pattern on the plywood, mark it, and cut it out. Then center the smaller pattern on the cut plywood, mark it, use the drill to make a hole in the center, large enough to accept the jigsaw blade, and cut the center out. You now have the window screen frame.
Mark a line about an inch from the bottom of the INSIDE of the wood frame, and cut the aluminum about 2" shorter than the frame is wide at that point. Glue securely in place with the cupped edge DOWN, so the top of the window glass will catch in the groove.
Cut the aluminum screening so the edges are about 1/2" inside the plywood edges, and clear of the h-strip. Use a wide stripe of hot glue to attach the edge near the alum strip, press into place, and let cool completely. Once secure, glue the other edges and let sit until hard.
Roll the window up about an inch, set the aluminum groove oner it, roll the window higher so the top of the screen frame fits into the groove for the glass.
Remember to flip the frame when applying the screening to the second/opposite frame.
Don't use nylon screening.