Hi All
I made one of these after reading a post I believe from Adam a few months ago now. If you have access to the equipment a very simple procedure, but even if not, "a get you by one" could be as simple as a hole, the size you want the dowel to be, drilled through a steel plate. The thicker the plate the better really up to about 10m/m. I made one from tool steel and put about 8 holes in it. The plate was about 6m/m thick and you drill two holes for each hole. One hole is about half a m/m bigger than the finish size and stops about 1mm before going right through. If I remember correctly 2,3,4,5,6,8,10,12, were the finish size holes I did, but I might be wrong. It was then hardened to 65 Rockwell and then I tempered it to about 60 Rockwell. It was then ground flat to give a nice sharp edge around the hole. I just take a piece of the wood that I want the dowel to be of, and make sure it has got a couple of m/m all around. It doesn't really matter if it is square or round and then tap it through the hole. I always tap it through a larger hole first and then tap it through the final size.
I believe it was Adam who posted this info in the first place and I can assure you it works perfectly to give you a dowel in whatever wood you require.
All the Best
John