I don't have x7 installed but hopefully this method from x8 may do.
On your page right click the search box > HTML Source
On the page that opens, amongst all the code you may see something like this
$('#site_search_1_input').keypress(function(event) { if ( event.keyCode == 13 ) window.location.href = 'index.html?site_search_results_1='+document.getElementById('site_search_1_input').value+'&depth=0&swr=false'; });
$('#site_search_1_button').click(function(event) { window.location.href = 'index.html?site_search_results_1='+document.getElementById('site_search_1_input').value+'&depth=0&swr=false'; });
You need to find the search box and button ID's, in this instance they are #site_search_1_input and #site_search_1_button
Copy the following and on your page do Insert > HTML Fragment, click on the page and click "Paste to Head"
<style>
#site_search_1_input, #site_search_1_button{
height: 40px !important;
font-size:24px;
}
</style>
This will make the search bar and button the same height.
Change the ID's to your ID's - DO NOT remove the comma or space after it.
Change the height to what you need
Change the font size to what you need
Reduce the size of the HTML Fragment and park it somewhere on the page.
Joe