The best tow is the remnant from processing flax to make linen thread. The tow from flax is harder and more coarse than the hemp, sisal or manila tow that is commonly offered. If you don't want to wait for an order to come in, you can get jute or hemp twine from a hobby shop or big box hardware store. Cut the twine in about 6" lengths and unravel the strands to single strands and you will have an acceptable tow.