Booster theme change search page input to match header search input

[minimalanimal]

Also hoping someone can help with this:

I would like the search input fields on my site, using booster theme, to match and be simple. I'm happy with the search input field in the header, but not so happy with the search input field on the page you land on from Search in the footer. 

The header search input looks like this: 

 

The search page (linked from footer) looks like this:

I was able to modify the submit button to use an underline style rather than a border style, but I don't have options to modify the input field. Having it look like the input field in the header would be great. I'd also be happy if it were all an underline, like this:

It just needs to be graphically clean and simple to align with my brand. 

Thank you!