this is the heart of the problem and not a good way to set up the database.
you should have only one items table in your database.
in the items table, you can create a company column to define the company the item belongs to, much like you would do with category column.
your wish list table should store minimal data, a primary key ID, the Item ID from the items table, and the Users ID who added the item.
all of the specifics of the item should be stored in the item table.
If you need help in setting this up, we can assist through a premiere support appointment: