Ron,
Harbor Models in California has line, lines made up, and tow lines. 3 + 5/64th inch which is just under and over 1.8mm.
https://www.harbormodels.com/chainrope.html

Hi Ron
If you have Amazon in Canada I see that they have stockists that supply 2mm blue polystyrene rope in small quantities that may suit.
good hunting
dave976

Hi, search for
Blue polypropylene twine 1.8mm in diameter. Here in the UK, hardware stores stock it