How to change the button type

Hello everyone. I changed the templates full-page-search.hbs and search-advanced-options.hbs

I want to change the icon in the button

<div class="control-group pull-left">
<label class="control-label" for="search-in-category">{{i18n "search.advanced.in_category.label"}}</label>
<div class="controls">
    onChange=(action "onChangeSearchTermForCategory")
Now it looks like this

I want it to look like this

I know how to replace icons. But here you need to change the button type. Please tell me how to do this?