I suffer from a tremendous amount of food allergies and I'm sick a lot from even the smallest amount of food bacteria, this of course requires re-hydration quite often. I come from a family of doctors, and most recently my new sister in law finished residency, she gives me the IV's at home now. (previously my mother did)
At any rate you can get IV saline here in Colorado from some of the bigger pharmacies, but you need a doctor or an IV certified technician (not sure if that's the right title) to purchase it. They also do not sell the needle/shunt/catheter thing here without a doctor as well, not sure if that's a local law or not.
You can also buy it online as well, with the needle if you like from a lot of places. I've seen people pack them in survival kits when hiking. But I could never give myself the needle.
Amazon.com: Baxter Saline 0.9% 500ml, Sodium Chloride, IV Bag, USP: Health & Personal Care