Boy, are you in luck. I have found that the best line to power pulley driven watch tools with is thin monofilament fishing line. Since you mentioned that you like to go fly fishing, you probably have a short piece of line in your fishing box already. Just make sure that you use the thin light (5 or 10 pound) line as the thicker line is too stiff to work well with a small pulley. The bow that I am happy with is the standard Bergeon bow that can be purchased on the internet (Ebay) for about $50.00 dollars. There is no real magic to this item as long as it turns the pulley, it is doing what it is supposed to do. If you don’t want to purchase a manufactured bow you can make your own. If it does the job and you feel comfortable with it then it is all that is needed to do the job.