Interstate document signature for touchscreen in to existing web app. Replace existing mouse signature field (does not work on touch screen.

I need you to develop some software for me. I would like this software to be developed to work with / integrate with an existing web app using PHP. I need a signature field so my clients can sign documents with their finger on a smart phone or tablet. Existing application only works with mouse and is not suited to my needs. There is a signature field and a document *.png the clients review already all I need is the option for signing on a smart phone with your finger. In the attached videos I have an example Of the facility that is currently loaded to my website and what I would prefer is in the second video.