OT: Looking for degausser/magnetic tape eraser

[Michael ODonnell]

Seriously:

   http://www.unitednuclear.com/magnets.htm

...and you'll have some fun, if dangerous, toys to play with, too.

I don't know that they're officially represented as being appropriate
for your specific purpose but some of them are so dangerously powerful
you can find pictures on the WWW of smashed fingers resulting from
mishandling them.  Woo-hoo!!