If you can't find locust thorns, you can try using toothpicks. The box I have now are about 5/64" round, but I have used 1/16 square toothpicks in the past by drilling a 1/16" hole and tapping them in - the corners sheer off and make a very nice fit. Toothpicks also come with tapered ends, you can get two pegs out of each tooth pick. I break off the tips, leaving just a small amount of taper remaining to get them started in the hole, then tap them in. The only drawback is that they tend to break off if you are not careful or the fit is too tight - keeping them short helps with this.