How to use articles in parentheses?

Do I need to use an article for the option word in parentheses?

If you want to create a new design of a handle (flag), the outer

diameter of the casing can be changed in the place of possible
junction with a handle (diverter).

or

If you want to create a new design of a handle (a flag), the outer
diameter of the casing can be changed in the place of possible
junction with a handle (a diverter).

or even

If you want to create a new design of a handle (or flag), the outer
diameter of the casing can be changed in the place of possible
junction with a handle (or diverter).