Well, I have been happy with the quality of all the Gransfors, Hultafors and Wetterlings that I have handled, certainly from a handle point of view. I have heard some people complain that the particular example they mail ordered wasn't as good as expected, but then I have also heard experienced people state that the grain orientation, which so irks some, isn't as important as is often suggested. So, a Google search for "Gransfors hickory hanldes" turns up a number, some of which sell handles for a number of premium and semi-premium brands. Other shops sell Smedberg handles, which can certainly be good.
Good suppliers are the norm, rather than the exception. Of course, I guess it depends what one means by "good", I have not had to call and talk to anyone at any of those, other than Greenwood, so couldn't say how their over-the-phone advice on tool selection is, but email questions have always been answered well and promptly and goods have always arrived safely and swiftly.
Although, when I bought handles from Pollards hardware of Bletchley (no longer open), one Faithful handle was hickory, as marked, and the two smaller un-marked handles were actually ash. Grain was spot on vertical through all three, but there were others there that were not so straight. The hickory was £20, and that was over 6 years ago.
Granted I tend to make mine, but whenever I do buy ready made axe (or other tool handles) I go to a local hardware store or agricultural supplier. Like the others have said, you can inspect the handle yourself to ensure straightness/grain/size are correct or to your liking. Most of them these days are hickory but you'll sometimes find ash still.
Unless you are replacing like with like on a particular brand (such as gransfors), then I would always prefer to go to a shop than buy online. If nothing else, you'll get the right size! People these days (thanks internet!) are overly picky about silly things like grain orientation, which is only a real issue with very curvy patterns and larger axes. I've never broken an axe handle due to the grain orientation, only from where it runs out the side. Same with having to be hickory. Ash and elm have been good enough for axes in Europe for hundreds of thousands of years, so they are good enough for me without having to transport them around the globe!
Dave makes a good point actually (though I disagree about blaming it on the internet - Kochanski, Mason, Kephart and Jaeger all talk about straight end-grain ) - grain that runs straight along the handle and doesn't run out of the side is more important. On a long handle with a heavy axe you will feel the difference in spring depending on whether the grain runs horizontal or vertical down the wood but on most practical axes it makes no difference at all. I make most of my handles and, in an emergency, I have made handles out oak, hazel, wych elm and cherry (and other wood) and they have all worked perfectly well and lasted just as long as my ash handles
I totally agree with Dave about using 'home grown' wood. At one time, nearly all axe handles in the UK would have been made of ash. For all practical uses it's as good as hickory so don't turn it down if you find it.
If you go on the Faithfull Tools site there's a stockist finder map and you can see what merchants around you stock their range.