You just right click the item to show it's properties and then click on the icon for the item in the item stats window. That will send a link to your chat window if that is what you were asking about.
Sounds like you are making some interesting progress on putting the string into the say link. I figured it wouldn't be too hard to get the string in there. But, getting it out correctly would be the hard part. Maybe you can change it slightly to have it make the NPC do a say message with whatever it things the string from the say link is. That should work to help debug what is happening when you click the link.
Since the packet breaks down the link into the ItemViewRequest_Structure for use in the link click handling, the string that you put in there would be split into multiple chunks. Then they just need to be put back together into a string that we can use. Maybe that wouldn't be all that hard to do afterall. We would need to get the info in Hex form, and then convert it from hex into a section of a string. Then, just create a string by adding them all together end-to-end back into 1 string.
If you get time to post what you have so far, I could look at the packet being sent by the client and see if it is sending the right string. If so, then it probably just isn't being put back together properly after it gets to the link click handling. If you are too busy though, no rush. This isn't high priority or anything