Custom field at the Item/Location level

Hi;

On an item record there are fields at the item/location level such as location on hand. It is not defined (at least at the UI level) as sub list, just field on the item table. When using multi location inventory, if you use location on hand on a search, you will get a line per item/location combination.

I am looking to add a custom field at that item/location level. Adding a custom item field will add it only at the item level, not item/location level. Is it possible to add a custom field at that level? The alternative will be to create a custom table with item and location fields both defined as parent. I would like to avoid that if possible and use existing database structure.