The two suggestions above were the two I was thinking of. I also like bath blankets. Flannel works well for them. Make them like very large receiving blankets. 1 yd x 45" wide! The perfect size. I made about 20 of them for my last grandson and my daughter is still using them and he just turned 4, 2 days ago. Now of course they are used for other things.
They are great to swaddle a baby with too, And they are large enough unlike receiving blankets you might buy. They work for both uses. Winter babies need more than spring/summer babies.