How to add quantity add-to-cart textbox to _ProductBox.cshtml ?

NC 3.90

I have created a template for category CategoryTemplate.ProductsInGridOrLines_custom.cshtml,
then dublicated _ProductBox.cshtml and called it _ProductBox_custom.cshtml,
added _ProductBox_custom.cshtml to CategoryTemplate.ProductsInGridOrLines_custom.cshtml

How can I add textbox (input type=number) to _ProductBox_custom.cshtml same like in ProductTemplate.Grouped.cshtml

Thanks in advance.