Use a national chain like Target/Walmart regularly for your Rx needs. Then, when traveling, you can go to another Target/Walmart store and get what you need. They simply transfer your account from your "home" store to their store. When you return "home", your Rxs' simply get transferred back. That has been our (many year) experience with Target.
If you use a local indie store for your Rx, wherever you are can also do the same thing....the new pharmacy can call your "home" pharmacy and you can then get whatever Rx you need. That ALSO has been our experience.
Of course, we do not (yet) use narcotics...that MIGHT be a different story. Time for you to investigate via your pharmacy, your insurance company and your doctor.
g'uck!