If you're going to use any injectable gear, then of course you're going to need some "darts." You can pick up syringes at your local pharmacy unless your state has certain restrictions. Also, you can purchase needles online. Just do a little searching around and you'll find several places that'll hook you up. Syringes will run you around 50 cents apiece. Note that it'll be more difficult to obtain needles (at least from the larger, more "legit" companies) if you live in California and Illinois. You'll usually need a doctor's prescription in those states. Still, if you look around enough, you can get what you need.
Steroid use is on the rise in Australia. Recent figures from the Australian Crime Commission show that the number of steroid-linked arrests and seizures hit a record high in 2011-12. Data from the latest Australian Needle Syringe Program survey showed almost three-quarters of new needle drug users in NSW took image and performance enhancing drugs, predominantly steroids. In November last year, youth workers in Melbourne were reported as saying the number of illegal steroid users obtaining free injecting equipment is increasing, particularly among young men using late-night mobile services.