http://jubileeinstruments.messianic-webhosting.com/prctlowd.htm
I believe they also have some of thier earlier pvc series whistles too, for about 29 bucks as I remember. The page is hard to find though. I can’t find the link. Seems like I just stumbled on it. It’s the same series he shows how to make in the book. That’s still a pretty inexpensive whistle, and may be better than the 18$ one.