I haven't found any that really helped me, but some other people here have had better experiences. Maybe they'll chime in.
As far as measured reduction in radio signal inside the canopy, the one I have that really works is made from uncoated aluminum screen that I bought at Lowe's and 'laced' together with galvanized steel bailing wire. (It's six-sided, i.e. it wraps around under the mattress.)
If you want to reduce low frequencies like 60 Hz, you need a steel enclosure and it's likely to be heavy and a little pricey (~$200 US for the thinnest sheet metal).