Where can i get a new liner for my american m1 helmet shell?

i want to be able to wear it comfortably. i need it to be as cheep as possible, the helmet is a swivel bale m1 i got from a friend. its got a small dent in the top and i wanted to be able to wear it. it has a heat temperature stamp on the inside. it seems to be a world war two era one. still sturdy and only has a tiny amount of rust. and still has some of its origional paint. all i have unfortunately is the helmet shell. the metal part. its incredibly difficult to wear without padding for my head. lol. does the liner just attach on the inside or do you have to "install" it?