Ripped string, broken plastic junction component

Hello, we have two older Pella brand windows in need of parts. I cannot locate a serial number on either windows unfortunately. On one window, the string for the blind ripped and I am looking for a replacement string. On the other window, the plastic piece that guides the string into the panes of glass has cracked. Part is stuck inside the panes so we would need to replace the entire plastic junction. Any assistance is appreciated.