We and several customers have had great success adhering to the nickel-plating using Loctite 39205 (an acrylic adhesive) with Loctite 7380 activator.  A Loctite representative also recommended Loctite 3032 (a 2-part acrylic adhesive) with Loctite primer 770.  For more commonly found adhesives, we have also had great results using many kinds of epoxy, often sold as "5-minute" epoxy. "Liquid Nails" and "Gorilla Glue" can also work well, and are available in most hardware and home supply stores.  It does help to scratch the surface of the plating lightly with sandpaper or other abrasive prior to applying the adhesive.  For more information, read our in-depth article: Sticky Business: How to Glue Neodymium Magnets.