At least one touchscreen of the correct size exists: the one that was used in Microsoft’s 13.5" Surface Laptop until the current (7th) generation. Generations 1 through 6 had the same size display; it’s exactly the same size, aspect ratio, and resolution as the original Framework display (not the 2.8K one). Like the 2.8K display, it has rounded corners. The new Surface Laptop display is slightly larger (13.8") but the same resolution.
Whether that display is available for Framework to buy is another question. Microsoft may have had an exclusive deal on it.