You want to go to www.bricklink.com
It is an online marketplace for used an new LEGO pieces.
They mostly use the part numbers stamped on the plastic pieces for their
catalog but things like string get assigned special codes. In this case “x77” is
used for string and additional codes are appended to that for different
variations (and lengths). Try a catalog search using “x77*” to catch them all
This is also a great resource for special wheels and other parts!
As a side note, using string to lift things may or may not work well. There
are other options such as a chain drive or worm gear that they may wish to think
Sent: Tuesday, October 04, 2011 8:57 AM
Subject: [VADCFLL-L] Lego String