Have you tried freezer suits? With matching boots?
They are absolutely awesome, and the perfect thing for observing during the winter months. They're becoming a more common accessory and more and more people at SPSP (for example) are walking around in them.
Get them off Geoff (GTB_an_Owl) at
http://www.gtbastrowise.com.au/
I use mine at home every night while imaging Jupiter at 4am.