How to Remove the Magnifying Glass from the Sidebar Widget?

I've been searching the forums and reading related topics but I am stuck on that magnifying glass.

Is it possible to use CSS to change the submit button so that it does not use the deafult magnifying glass image but is just a text button instead? I've don't know enough CSS to know if it's possible to override the src of the input field.

I am looking for a solution that does not involve me changing the code.

Default html looks like this:
ps-- making this an editable option in the widget field would be super helpful!