Made myself a Hammock sock and it gave me a minimum of 10+ degrees inside my hammock. The more the wind blows the more effective it is.
If you dont have the proper materials you can rig a hammock sock up with just 2 bed sheets attached to each other making a tube or sock(however you want to look at it). If your hard pressed for time just use a stapler to attached the sheets together. You can pop the staples later and redeem your sheets again. You need around 90 inches of total fabric length to make a small hammock sock. 100 inches would be better.