Are you wanting cheap of nice really nice?
You can take some silver (real silver) wire, drill a matching hole through the tusk, wrap the wire around the tusk about 1/2 inch up to the end and using silver or gold solder and wrap the wire and heat just enough to melt it into the wire.
http://www.jewelrysupply.com/jewelry_findings/14_karat/solder.htmlThere are some cheaper solder that only look gold.