I was at a thrift store not long ago and spotted a couple of simple wooden candle holders. I happened to have a key chain measuring tape with me and discovered the hole in the holder was about 21mm. So I bought them both for $2.00 total and then ordered a 20mm pure Badger knot from eBay for $5.50. After using a dremel to cut off the base of one of the candle holders, I polished it up and sealed the base with epoxy then drilled out the hole a little for the knot to fit properly. I set the knot with JB Weld wood epoxy and let it cure for a full 48 hours. Here's the result! I still have one leftover candle holder but no extra knot yet to make a second brush.