I have used OR Flex-Tex gaiters for years. What has worked for me is to thread the flat lace thru a piece of clear plastic tubing, the smallest diameter that the cord can by threaded thru. This has lasted for 100's of miles and can be changed when it starts to wear out.
To thread the flat lace, I first run a stiff wire thru the tubing and crimp it to the lace. It can then be pulled thru and the wire removed.