How do I change the size of calendar icon in airDatepicker from shinyWidget?

I use airDatepicker from shinyWidget on my dashboard:

Here

I have succesfully change the size of the input container as shown in the picture, but not the container of calendar icon (the box where shinywidget place the calendar icon). What I wanted to change is the box encircled in yellow, not the icon itself which I mark with red border.

How do I do it? Thank you.