Sidebar search widget size

Hi!

On my right sidebar (on Blog and posts), I have the search widget. It almost fills the width on desktop, but on tablet and mobile (when shifted below the main content) it becomes narrower than the rest of the items in the sidebar which looks weird. I've changed the justification to center to fixe it somewhat, but I really would like it to be as wide as the rest of the sidebar on mobile and tablet also.

See https://www.stag1.ikigai.se/valmaende/fem-rad-for-julefrid-i-pandemitider/

How can I fix this?

BTW: I might have discovered a bug: The search entry field in the widget displays with a border radius on IOS-devices. I managed to correct this with:

.search-field {
    -webkit-appearance: none;
     border-radius: 0;
}

I hope this was a correct way.

Best regards,

/Ola