Hi there, I can feel your pain being a fellow minnesotan. I have a little chief electric smoker, and the walls are paper thin, and maintaining heat in the cold was a concern. I smoke primarily snack sticks, summer sausage, and jerky, so most of my stuff is under 170 degrees or so.
So, if you are doing low temp type things, one fix may be like what i did. I got a roll of this material called reflectix. You can buy it at menards or home depot and it is about $10 a roll. It is essentially bubble wrap with a foil covering. It does a great job on my little chief, and i can maintain 160 in 10 degree weather. In fact, i'll be smoking a pile of venison sausage tomorrow for the holiday season.
Now, that being said, realize that the reflectix only is tolerant of heat to about 180 degrees, and being that the ECB has a 1500 watt heating element, it may get way too hot down by where the element is, and may melt the stuff at high temperatures.
My brother has an ECB and what he does for the winter months (he does primarily hotter stuff like boston butts, brisket etc) is he has a 55 gallon rain barrel that he wrapped with a water heater blanket. he said he can get up over 200 degrees with that type of contraption. Just make sure that you cut a hole in the top so the smoke can escape. This would probably be a much safer way to go for the ECB.
He got his barrel from the beverage bottling company in his hometown, and if you live in the twin cities area, there are a lot of those places around. Otherwise, i understand car washes get their soap in these types of barrels, and might give you one for free. Or, if all else fails, I checked craigslist in the twin cities, and there are a number of people that are selling these plastic barrels for about $15. this is a pretty easy fix that will be relatively cheap.
Anyhow, If this doesn't work for you, the guys on these boards are really great, and i'm sure they will know exactly what to do to help get you up and running. Good Luck!!!