A national chain should work fine for you. I’m usually gone for a month at a time and sometimes two and I have to refill. I use Walgreen's and they can access my local records and refill with no problem. Two qualifiers. Don’t use mail, I did that in FL and specifically told them to mail to an address there. They sent it to my home in AZ and it was a major PITA to sort out with the insurance company.
Also, Walgreen's tracks your refills and when you’re back home you may get an automated message about refilling your med. I did that and at the end of the message it said my prescription would be ready to pick up the next day at the pharmacy in Jacksonville, FL- the last place I got a refill. I told the local pharmacist to tell their IT guy his system would work better if he identified the pharmacy up front rather than finding out after the fact where the prescription was going. Other than that, though, you should have no problem getting your refills.