Optimal source for "Narcan"/Nalaxone?

www.amazon.com

Amazon.com: Padagis Naloxone HCI Nasal Spray, 4 mg – Emergency Treatment for Opioid Overdose - Rapid-Response Opioid Overdose Reversal, 2 Dose Single Use Nasal Spray : Health & Household

Trying to have some of this stuff around in case I'm ever in position to help someone struggling with opioid addictions. Is there a reputable source where I can buy around 15-20 applicators and be sure it is "high-quality", etc