I'm waiting ......
Encase the thing in a superconducting box. The Meissner effect will do the job.
... if you *really* need superior magnetic shielding beyond that which mu metal would yield, then your recourse might lie in the use of a super-conducting material ...To quote Richard Barrans Jr., Ph.D.: http://newton.dep.anl.gov/askasci/phy99/phy99x89.htm
"Superconductors exclude a magnetic field entirely. That is the physical basis for "magnetic levitation": magnetic fields actually repel superconductors."