I’ve thought of refilling mine but two things prevent me. One: I just don’t use enough 1 pounders to merit the need for them. I currently have about a dozen store bought bottles that are still full. Two: the rust is too high for the reward.
Flame King makes a refillable one pounder but they are expensive and they look just like the un-refillable ones. I have a five pounder which I occasionally use. It can be refilled anywhere.