There is a repair kit that comes with the string, spring and plastic "bobbins". Have seen these at Camping World, various RV places and on Amazon. "Shade Repair Kit" may be the name. YouTube will also have some videos of repairing the shade.
2013 F-350 CC SB 2WD 6.7PS
2013 Eagle Premier 351 RLTS
-SOLD- 2012 X23B
-SOLD- 2003 Ford Expedition 5.4, Bilstein shocks