Thank you for your reply Redzaku.
Yes, the Paratroopers did have a M1 helmet (i.e. M-1C) customized for their parachute jumping needs. Look at the helmet picture in this
link and notice the chin strap arrangement.
I have seen helmets with the plastic liner like the $40 one you sent me in your link. In my experience they don't last well in re-enactment field operations, sorry.
Thank you for your reply 666.
The ATF M1 helmet that you linked will do very well, thanks! I didn't notice it at their site before.