Well, what are you looking for in particular? Oriental whole leaf is becoming readily available from Wholeleaf.com, Leafonly.com, and, uh, oh crap, forgot the other guys. Fairtradetobacco? Maybe.
Then, Find yourself some Red Virginia. One of those folks have red leaf by the pound for sale, or, another option is Pipesandcigars.com has a newish red Virginia ribbon, RC-1, that, with some tweeking, can provide a reasonable base for your blends.
Or, the option I generally employ, start growing and processing your own. But, unless you're willing to wait a few years for your stuff to mature, that's the Long Game.
Hope this helps!