Magnetic cabinet latches are available from the Woodworkers Store catalog,
4365 Willow Drive, Medina, MN 55340, (1-800-279-4441) and at 14 company
stores throughout the U.S.  They're on page 50, item #63164 for the lock
($5.25./$4.74 for 4 or more) and item #63172 for the magnetic key ($5.95
ea.),one key activates all locks.  The lock is fully concealed inside the
door, has a template to mark the installation location, and installs with a
screwdriver.  It works on doors 1/2" to 1 1/4" thick.  There may be similar
locks other places, but this is the first one I found in my catalog.
[Posted in FML issue 1743]