Creating a new product, trying to use quick create form for Unit Group and Default Unit

How can I add a Quick Create form for Unit Group and Default Unit?

Both entities have the Allow Quick Create option disabled and I am unable to add a new form i.e. there is no add new button like there is for Account and Contact.

If I cannot create a new Quick Create form, how can I disable the "New" option in the lookup that brings up the Quick Create form.  Currently it brings up nothing and the user has to "X" out of a window that has nothing in it.

Thanks.