On Ebay, appears to have been newly listed. I remember these well, my grandmother liked to use them. I could hear them clanking on the fins of her Whirlpool bakelite Surgilator until they dissolved.
http://www.ebay.com/itm/Vintage-Sal...189?pt=LH_DefaultDomain_0&hash=item3a7f9e74cd
http://www.ebay.com/itm/Vintage-Sal...189?pt=LH_DefaultDomain_0&hash=item3a7f9e74cd