I have a ~0F "very warm" bag that does not have a "cinch" draft collar. I cinch down the chin and hood, but when I move around I can still suck a little cold air into the bag (and I assume it constantly lets a little warm air out throughout the night).

I know nothing replaces a good draft collar, but any thoughts on a lightweight option (e.g. down vest) that I could use to block the draft from occuring? If I lay a fleece blanket across my chest it does the trick, just need a lighter weight option. Thanks!