Update
I've been successful finding nylon (and silk) thread in almost every color one might desire and at reasonable cost.
Thread suppliers, bead and jewelry suppliers, as well as fishing rod supply vendors all are sources and can be found through Google searches.
My lingering question though is: What size is generally used? In the letter system, I have been told Size EE and Size F are correct and conversely I have been told those two sizes are incorrect and that Size FFF is what should be used.
(There is also a numerical coding system which I have not explored.)
Does anyone here have an opinion, or better yet, experience in using specific thread sizes?
Once again, thanks in advance for your help and advice.
Jay