I bought a sauna suit from target for $10. Bell is the manufacturer. I think they're seven bucks at wally world. The top (size medium) weighs 7.8 oz and the bottom is 6.25. Not bad considering the equivalents from RBH designs weigh nearly double, and cost over $100 each for both top and bottom – albeit they are much nicer.
My sauna suit packs down small and is functional. The durability is reasonable. The fit is about what you would expect a cheap plastic garment to be. I haven't worn mine as an active layer yet since it's not really what I bought it for, plus I think there would be some comfort and fit issues when trying to move in it.
Eventually I'd like to sew my own silnylon suit to customize the fit and probably drop some weight. Though for $10 and instant gratification I certainly have no regrets about this pick up. It is a very cheap, efficient way to boost your sleep system temperature rating.