netbox/netbox/templates/ipam/inc/toggle_available.html

{% load helpers %}
{% if show_available is not None %}
    <div class="pull-right">
        <div class="btn-group" role="group">
            <a href="{{ request.path }}{% querystring request show_available='true' %}" class="btn btn-default{% if show_available %} active disabled{% endif %}">Show available</a>
            <a href="{{ request.path }}{% querystring request show_available='false' %}" class="btn btn-default{% if not show_available %} active disabled{% endif %}">Hide available</a>
        </div>
    </div>
{% endif %}