Thanks John. Looks like a great resource. Hopefully some company in the US will opt to carry the products (their home page notes 'made in Canada' and has a message about tariffis), and save us from having to become experts on international trade law.
On their site, they have sizes down to .25 mm (.009"), which scale out to a touch under an inch and a half in N scale. Anything smaller than that, and I for one would not be able to make out the twist in the rope.

In HO, it would be just a bit larger than 3/4 scale inches- appropriate for rigging the flies of an HO scale theater or more mundane duties, like tying down a load in a pickup.