you need to edit the loot table entry for this
http://www.projecteq.net/
has a tool available for editing the database in a graphical format, i posted a detailed walkthru for installation of everything on their forums as well..
once you have it installed, select the loot tab
select the zone
select the mob
scroll down till u see the item you want it to have equipped, then click the edit box at the far right of it's row (whiteish blue box looking thingy)
on that page, change Equippped?: to yes
and save it