I was recently in Ottawa and went to the Lee Valley store there. To my surprise, they had both steel and brass round bar in various diameters up to about 3/8". All lenghts were about a foot long. One of their manufacturing facilities is on the same property there in Ottawa, so I suspect that these were just extra lengths left over from the shop. They didn't have partnumbers or anything, just bins and cheap prices (like 20 cents per bar).
No idea if they have it at my local Lee Valley, but it's worth asking....
Murray