Reinforcing yarn sold sep?

Does anyone know where to get reinforcing yarn for socks sold separately from the sock yarn? I know JaWoll sells their sock yarn with reindforcing yarn included, but I need some for some yarn I happen to have on hand.

I have found it at my LYS but you can also get just the Jawoll reinforcing thread at Yarnmarket.com. (http://www.yarnmarket.com/yarn/Lang_Yarn-Jawoll_Reinforcement_Thread_Yarn-3475.html)

Hope that helps.

I read some where about the use of Wooly Nylon thread for reinforcement and adding some elasticity to the piece. Wooly Nylon is available at Joann Fabrics and come in a variety of colors.

You can also find the Jawoll reinforcement thread at www. patternworks.com