I’v played the Celtic flute a lot, pipes, and recorders. My whistle is the standard metal tube with a plastic fipple and high D. Do they make a tapered bore whistle. It seems like tapered bore woodwinds have a better tone quality, but maybe it is my playing. Where can I get a conical bore whistle, if there is such a thing?
Nelson
There is. Clarke on the low end of the price range, Shaw in the low-middle, Copeland on the high end.
On the wooden end of things there is Bleazey. I own three Bleazeys; High D, Low G and Low D. They are very nice, well built (solid) whistles. He also makes flutes (and recorders?). I am not sure if Grinters or Sweeneys are conical or not.
You should check out the whistle guides for inexpensive and high-end on this website. There is alot of information there which will be a great help for you.
Grinters are not. Swaynes are. I believe the new Sweethearts are, too (I know the old ones were), but I haven’t one to check.
Me! Oh, I thought you were looking for a tapered bore whistler…nevermind. 
Susatos are at least slightly tapered. Whether they are tapered enough to make much of any difference is debatable.