Nice stuff Don Luis!
Roadrunner,
Another place to look for ideas is tack stuff for riding. Very nice stuff, often made from leather strips or laces. Haven't tried that myself.
For smaller diameters the best stuff I found was very tightly single-braided (as opposed to stretchy and tubular) green synthetic line sold for making or repairing comercial fishing nets. Seine twine it seems to be called. You want the real stuff, lots of places call anything siene twine. It is made to be knotted and hold the knots, water resitance is obvious. Not a lot of color selection, typically white or green. This may be hard to find some places. Look on the 'net (hee-hee), or go to a marine store, and there may be some other choices than the jacketed (kenrmantle or double-braided) modern lines employed for rigging.
This place has the seine twine up to diameter of 0.125 inch, and tells you what the size numbers used to describe this product mean.
http://www.sterlingnets.com/twine.html
This site describes some different ways of constructing cordage.
http://www.industrialrope.com/slctguide.html
A hard, very tightly woven or twisted line is easier to tighten and work in my experience, and when waxed it is possible to draw the knots up really tight and permanent creating a surprising hard and tough covering or braid. For a handle covering, even good old hemp could be used followed by a couple dips in thin epoxy instead of the tar or pitch that used to be used. "Hempcarta"?
As far as lanyards or fobs go, good old twisted lines provide the opportunity of employing knots tied with the separated strands-many are quite decorative and designed to prevent the ends of the line from unwinding. They can also be tied with multiple strands of other kinds of line.
Don't have a camera, but here are a couple pix -- I'm suprised that I don't see much of any use of what are known as coachwhipping or needle hitching for knife handles.
http://www.igkt.net/galleries/tools.html
[urlg]http://www.knotwork.ca/knots/knots/page3.html[/url]
Any of the techniques use for making bellropes or chest beckets (handles) could (and were) adapted to make knife handles (or fob-like lanyards). Just knot around the tang (possibly previously built up by a simple wrapping) instead of a piece of large line.
This site has some nice examples of bellropes or beckets for sale so you can get an idea.
http://www.marlinespike.com/order.html