Allow user to Add own Option to drop down - but not permanently

Similar to any OTHER option in a multiple choice drop down, I need someone to be able to choose Other, then enter what that Other value is as text.

Creating a new dropdown option "Other" then a new text field to enter "other" is ok, but clunky.

The form option "Allow user to add option" works great - EXCEPT I dont want that newly added option to be a permanent choice in the drop down choices, just entered in that users record then forgotten after submission. I need the Allow user to Add Option to work as it does but NOT remain a permanent option in the form.

In a forum post a user kindly offered a solution but its kinda complex when making it an option natievley would be easier.