Check the bottom rail for the day/night shade manufacturer. Mine were 8 yrs old when strings broke on 2 shades. I removed the shades (that was enough of a challenge for me), sent them to the manufacturer and they repaired them - free. I did pay for shipping - about $15.
'02 KOUNTRY STAR DP
2012 HONDA FIT "PUMPKINMOBILE"
GILLIGAN- 1ST MATE CAT - 3 HR TOUR
It takes more effort to shop for replacement blinds or ship them off for repair as compared to re-stringing IMHO. We had one break on our last trip out. When we got to the campground, we re-strung the shade in about 20 minutes. We use a long sewing needle to guide the string and it works real well.
A broken string isn't that hard to change it just looks that way. If you take it apart and watch how you take it apart it goes back the same way. I have replaced them several times and it isn't that hard. You can go on the web and get directions.