eBay has an adapter to refill portable butane bottles for $8.00 with free shipping.
I'd about given up finding one of these and threw away a lot of empty bottles a few years ago. It only took two days to get here from California, over 1000 miles away. eBay is great for finding things, and shipping cost are affordable, and I don't have to sign up for prime like amazon to get affordable shipping.
I'm going to be looking in trash cans for empty bottles when I go camping this year.
YouTube has videos that show how to fill the bottles, and has videos for doing almost everything.