Islanders custom tackle has some high quality bags that are designed for use on the boat. One is even shaped like a chair. These will be more expensive than a garden ridge bean bag. But, should be much more durable if you are planning to get a lot of use out of it.
Just went through this. None of the local League City shops had anything in stock - even the guy that used to have 'em sitting next to the road said his supplier stopped selling them. Ended up ordering from Target On Line. (Not in stock in our local store) $19.99 for their "lounger", very comfortable. In fact, liked the first 2 so much, we ordered a third one.