Pella Screen Spline

I have what I think is a Pella sliding glass door and the sliding screen door is located on the inside of the unit. The current spline is a square variety that I can no longer locate and I cannot reuse what I had before since it was very old and no longer sticking to the spline groove. Any ideas where to get square spline or a replacement door for the inside? The approximate measurements of the screen door.... 37.5in x 80.5in x 3/4in. Thank you for any help.