for branches, try
Manzanita Burlworks - The Source for Quality Handcrafted Manzanita Products . if you call them you can specify exactly what you're looking for. they're very helpful, and very affordable! shipping is cheap, too.
as for fake plants and such, i'd suggest going to an area craft store. TONS of options, very inexpensive. with the plant vines, be sure they're not made of small plastic rings linked to eachother. snakes can get caught in these.
not really sure about vines, though. try
Reptile Supplies and Exotic Animals they've got a pretty good selection, and decent prices.