Maintaining strict one-to-one association between terms and custom posts

I’m building an inventory system where inventory items have their own page but where standard WordPress post post types can also be tagged with these inventory items. As far as I understand, this means I must implement both a custom post type (inventory) to provide each item’s page and a custom, non-hierarchical taxonomy (inventory_item) to represent the relationships between posts in the post post type and pages in the inventory post type. Each custom post type post would be associated with exactly one inventory_item term.