I have been rebuilding some sets piecemeal for my own collection and several times now I have need lego rope. being that it's just for me and doesn't need to be 100% original I have been trying to find good replacement string/cord/rope for the lego ropes and I just have not been having any luck. everything is ether too thin or too thick. The lego ropes do come in several different thicknesses and materials which also makes it a bit challenging. so what do you all do when you need some lego rope? it's just hard to justify the prices on the original thing...

The best sources for replacement Lego strings I've found have always been in commercial fabric & weaver supply shops or the "loom store" (but I think they are just a one-off local company).  They carry "cotton thread" spools in numerous gauges & colours that can be a nearly perfect match. You can replace with better colours to match your build such as realistic brown ropes, tan-green anchor lines etc. (if you're not a purist of course)   If you have a sample of the thread you are trying to replicate they can probably order the exact gage/colour you need. 

 

You might try searching for "cotton thread suppliers" or perhaps "nylon thread suppliers" with more location specific luck.

I'll give that a try, thanks!