I suppose you are left to Google for the answer to your specific question
about finding a particular material.
I'll just give you some response in saying that, perhaps in more *casual* way,
my whipping of various mostly "small stuff" (1/2" and smaller) uses whatever
tiny stuff looks interesting -- i.p., monofilament nylon fishline of various strengths,
mason line (150# strength typically, and bright colors), and even teabag strings (!)
-- oh, and more recently, various widths of fibrillated polypropylene yarns, which
is a nice use for stuff I had little regard for, previously (its flat profile enabling
some novel whipping structures).
The monofilament whipping can look very solid, abrasion-tough, and neat;
for that, I use an extended Strangle knot, having an extra crossing buried,
and about 7-8 overwraps (mason line in contrast, being more flexible, works
with 5-6), AND a sort of Common Whipping finish on one end (my way of
being cheap and not wasting material there, plus a security gain). The
Strangle is loosely tied (one needs to be able to tuck a bight of the working
end material through the overwraps), and then tightened, iteratively giving
it some compression, with pliers or by rolling it firmly, to try to work the
high tension on ends into the inner overwraps.
Typically, in laid rope, I'll want the whipping line to be thick enough to have
friction when the Strangle knot's buried crossings area set in the groove of
the lay.
--dl*
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