I would imagine that one might be able to continue selling these magnets via, say, a mail-order laboratory-supply store that caters to school science labs. Such stores carry lots of products that are dangerous in counterintuitive ways:

http://wardsci.com/product.asp?pn=IG0015551

Don't get the sodium metal wet or feed it after midnight!

But such products also aren't labeled like toys, or stocked in storefronts that also sell toys. They are labeled like industrial products and ship with MSDS sheets.

The problem is that killing the existing sales channels will likely kill the existing business, because the sales volume will drop by orders of magnitude.

Definitely agree.