Vocaloid items (it's to be assumed that you mean 'character items') are objects created by the fandom for a Vocaloid avatar to hold, the items are usually done in relation to a Vocaloids color theme or most popular fanon personality trait. However, it is the Crypton Vocaloids who hold the lead on these items; it eventually influenced fans to attempt to give items to other Vocaloids.
See Internet Meme page on Vocaloid Wiki to read about officially acknowledged items. Since the 'item war' page has been redirected, you can only view its history to see the ideas for items with other Vocaloids. Since these items are constantly argued about, the page was becoming a bit of an influence rather than a tracker for developing item ideas.