Another knitting needle question to add to the mix

I have a good question. I think. Maybe. Ok I had found a pattern for an blanket done on circular needles. I had gotten it 3/4 ths done and wasn't happy with it and took it apart. I know, I know. It wasn't big enough, it wound up being very small and I wanted it more than double the size it was coming out without making it in panels. It was an argyle winter pattern in green, orange, black and yellow. The pattern is from McCall's Needlework. My question is this: How big circular needles can you get for a blanket? These were a size 4, 36 inches. I don't know If I will have to make a pair or what. I will buy new yarn to make it again BTW!! It did come out gorgeous, just small, small, small. Have a good weekend Everyone!!! Fairwinner