Oogle around Shugs videos and his -40 exploits
https://www.youtube.com/user/shugemery

I would recommend the UGQ rental program as well...at least you will have what you need (you supply the TQ/Sleeping bag). At them low temps you DO NOT want to be DIY'ing without some serious testing to be sure you got it right especially when you hiking in a ways and a bail out is not right there.

A Dutch Hammock single layer is a good place to start and then spend the big $$$ on down UQ TQ rated for at least 0* from any of the vendors on here.
For a Tarp you can cheap out with a Wally World blue tarp

But do back yard test before you depart