Funny you mention this--- I've been writing up a thing on bucktail to post on here--- coming soon. It'll cover what to look for when buying, and a couple of different techniques for tying with it.
But here's some info.
For tying on larger hooks for salt water, pike/musky etc, look for bucktails sold as "Salt Water length"-- they typically run around $5 or so-- a little more than the normal ones sold for around $4.
The SW bucktails are longer in total length-- around 12-14 1/2" or so, and the hair length is longer-- tyoically 3 1/3-4" long. Regular bucktails are typically 9-10" long overall, with hair 3-3 1/2". You'll find the extra length of the hairs on a SW will come in handy on some flies, and of course you can always tie it in shorter for smaller flies.
The hair at the base of a bucktail tends to be thicker and more hollow than the hair in the upper 2/3's. As a result the hair at the base has a tendency to flare under thread tension when you bind it to the hook shank like hair from the body or belly of a a deer used in spinning to make bass bugs and "muddler' type heads.
If you are shopping for them yourself and have the opportunity to pick through them, look for long ones as opposed to short and squat ones, because the short and squat bucktails will have a great greater percentage of the thick hollow hair. The short squat ones also generally look short and squat because they have relatively short hair.
Here's some pics that might help:
On the left, a purple SW length bucktail, a "normal" chartreuse bucktail, and a short squat blue bucktail (to avoid):
Here's a pic of the individual hair from each of those bucktails, with the hair from the purple SW bucktail 4 1/2- 5", the chartreuse normal bucktail 3 1/2", and the hair from the blue short and squat one 2 3/4 - 3"
And here's a pic that illustrates how hair from different parts of the bucktail react under thread tension. At the rear of the hook some solid fine yellow bucktail from the upper 2/3 of a bucktail. Notice how it lays down flat with a minimum of flare. At the front of the hook, some thick, hollow white hair near the base of a bucktail-- notice how it flares under tension. There are ways to tame flaring hair with thread wraps and other methods, but this is a good example of how hair from the different parts of a bucktail behave.
As far as where to get them, hopefully your local shop - if you're lucky enough to have one, will carry SW bucktails-- or will order them for you.
I get mine from 2 places. Note that both sell both regular bucktails and SW length bucktails so you have to specify otherwise you'll get a regular bucktail.
Chris Helm at www.whitetailflytieing.com
Chris runs a one man operation with excellent quality materials-- he is THE MAN when it comes to all things deer hair. Excellent quality and service. Ordering is a little clunky because he doesn't have an e- commerce enabled website. But on the other hand, he has a 800 number and email and is very responsive--- and is extraordinarily helpful if you have questions. He's a pleasure to deal with. You can download his catalog as a pdf
I also use www.waterflies.com
Their site is more fully enabled so you can do the whole thing on line. They have a pretty good selection of SW tying materials. They are also very responsive and offer free shipping in the US.
I'm sure there are a lot of other excellent sources out there, but these are the 2 I use for SW bucktail- in fact I ordered from both today
Hope this helps-- I'll post a bunch of techniques for tying with BT, and some examples of flies that use different techniques soon.