Searching for NULL values in binary fields.

I have a binary field that I am searching against on the device format:
I can typically search for true or false values using Checkboxes, display lists in Combo Boxes or Radio buttons.
But I also need to search for NULL values and my 3 listed widgets do not allow for "NULL" searches on binary fields.
Would anyone have any suggestions.

I seem to remember that older SC/SM versions had checkboxes with a characteristic of clicking on it twice and it turned into a null search, but alas no more...