I found some offered on Etsy by a Canadian mom. She prices them at $8 shipped. The only catch is that you have to know what size you wear. I wear a 35" sized bow tie. Now to get that size you need to tie your bow tie to the length you like. Experienced bow tie wearers will know that even that is not exactly right. You need to consider the width of the tie, the way it hangs off your collar, if it projects forward and how far, thickness of the material, how tight you tie your bow tie, and width of your face. In other words, just go and tie one of a similar cloth and measure the desired length.
I purchased these sized bow ties from Ruffle-N-Tuck on Etsy.
Tartan in a Silk Wool Blend
Tomato Red in a Wool Flannel
Edited: to include the purchase details.