Showing spinner in Combo box options when the data is getting loaded

Hi All,
Is there a way to show a spinner on the empty option that gets displayed when the combo box gets expanded while the data fetch is happening.
Using OverlayBox I can show a spinner on top of the combo box. But is it possible to achieve the first use case.

try to set OverlayBox to combo’s popup
https://docs.webix.com/api__link__ui.combo_getpopup.html

Thank you for the suggestion