The biggest problem with what you are looking for is that the Turbine API only allows querying the Vault and Shared Storage when you are interacting with them. This is one of the reasons why AltInventory keeps track of so much information. For a search plugin to work it would have to have all of the inventory data that AltInventory keeps.
That said, the next version of AltInventory will have a simplified search window (as well as an option to turn off each type of panel for those you don't use to help with the "clutter"). The simplified search will allow you to quickly and easily search for all items matching a search phrase in all storage on all characters and is sortable and filterable by category the same as the inventory panel. It does not yet have a chat command interface but that is fairly easy to implement.
The drawback to waiting for the next version of AltInventory? Time. My development box is still dead and I have no idea when I will be able to replace or repair it.