The big box hardware stores all sell refill tanks. One hardware store nearby refills tanks, but it seemed like half the time they didn't have a propane guy available.
I finally just ended up driving to a depot site that sits on the pipeline and whose main business is trucking it to people who have big tanks for heating. They are also the only ones I found to charge by pound for a partial fill rather than a flat rate based on tank size.
I realized after I posted what the difference is between NH and OH.
Here in NH we have very limited natural gas pipelines. The closest one to my house is about 3 miles away and stops at our high school. Therefore, most residential central heating systems are fueled by heating oil or propane. I have oil forced hot water and a pellet stove insert in a fireplace.
Many newer houses have the big underground propane tanks. If I was building new, I would go with propane. So, there are many propane delivery companies in the area. The rail track behind my office services a propane delivery company about 8 miles west of here. They bring tanker cars to them often in the winter.
So, the local hardware store, lumber yard, landscape all have approximately 2000# tanks to refill 20# grill tanks.