Thats an idea. Hobby stores carry rare earth magnets that would work good, and they are strong, too...strong enough to securely fasten a hatch on a radio controlled boat going 60 MPH.
Heres a link for square ones, .75" x .75".
http://www.rare-earth-magnets.com/detail.aspx?ID=78
pull force of 9.05 lbs.!
Greg