Are you doing a western or WA handle? Experienced woodworker or more of a beginner?
There are lots of vendors for materials from here on the forums, to online, can even name a few places in the Bay area for you. Happy to point you to a few, but as for which wood - What you plan to make, what tools you have available, and experience woodworking will all factor in.
If this is tied to your other thread on the Forgie remake and you're going to stay with its western scales and not do a significant reshaping/reprofile..... you have a pretty broad range of woods to play with. Exotics or rare grain patterns will be harder to work without experience but on a western handle, buying blanks precut for scales isn't going to set you back so much that it's not worth experimenting with something you like.
My favorite woods to work with - for ease of use in carving/cutting etc - are walnut and cherry. Maple, if staying with domestic woods, is much harder to finish. For exotics, bubinga is pretty forgiving and great looking, as is pheasant wood. Rare exotics - rosewoods, ebonies, ziricote - all are very dense and challenging, not to mention significantly pricier. Similarly, really unusual grain patterns and burls can be tricky.
If you go with something exotic before you start working it, cautionary advice - do a quick check on wood-database to see about allergy or toxicity issues. Cocobolo, as an example, is pretty nasty stuff for some people. Redwood dust, for others is brutal.
This post probably ought to get moved to the Shop forum....but am glad to add more info for you when I have sense of what you're planning to make. Can send you few local suppliers as well.