Modify the Gravity Forms shortcode to add a button before the form, and hide the form until the button is clicked.

gravity.php

<?php
/**
 * Helper Functions for Gravity Forms.
 * @package Leaven
 */

add_filter( 'gform_shortcode_button', 'leaven_gravity_button_shortcode', 40, 3 );
/**
 * Add the "button" action to the gravityform shortcode
 * e.g. [gravityform id="1" action="button" text="button text"]
 * @param $shortcode_string
 * @param $attributes
 * @param $content
 *
 * @return string|void
 */
function leaven_gravity_button_shortcode( $shortcode_string, $attributes, $content ) {

	if ( 'button' !== $attributes['action'] ) {
		return $shortcode_string;
	}
	$defaults = array(
		'title'        => true,
		'description'  => false,
		'id'           => 0,
		'name'         => '',
		'field_values' => '',
		'tabindex'     => 1,
		'text'         => __( 'Click to open form', 'leaven' ),
	);
	$attributes = wp_parse_args( $attributes, $defaults );

	if ( $attributes['id'] < 1 ) {
		return __( 'Missing the ID attribute.', 'leaven' );
	}

	return leaven_build_gravity_button( $attributes );
}

/**
 * Build the button/form output.
 * @param $attributes array shortcode arguments
 *
 * @return string
 */
function leaven_build_gravity_button( $attributes ) {

	$form_id = absint( $attributes['id'] );
	$text    = esc_attr( $attributes['text'] );
	$onclick = "jQuery('#gravityform_button_{$form_id}, #gravityform_container_{$form_id}').slideToggle();";

	$html  = sprintf( '<button id="gravityform_button_%1$d" class="gravity_button" onclick="%2$s">%3$s</button>', esc_attr( $form_id ), $onclick, esc_attr( $text ) );
	$html .= sprintf( '<div id="gravityform_container_%1$d" class="gravity_container" style="display:none;">', esc_attr( $form_id ) );
	$html .= gravity_form( $form_id, $attributes['title'], $attributes['description'], false, $attributes['field_values'], true, $attributes['tabindex'], false );
	$html .= '</div>';

	return $html;
}

single-product.php

<?php

add_action( 'woocommerce_after_single_product_summary', 'leaven_add_gravity_button' );
/**
 * Add a "Request a Quote" button to all custom (non-purchasable) products.
 */
function leaven_add_gravity_button() {
	global $product;

	if ( $product->is_purchasable() ) {
		return;
	}

	$form_id = 1;
	$text    = __( 'Request a Quote', 'leaven' );

	gravity_form_enqueue_scripts( $form_id, true );
	echo do_shortcode( '[gravityform id="'.$form_id.'" text="'.$text.'" action="button"]' );
}

style.css

.no-js .gravity_button {
  display: none;
}

.no-js .gravity_container {
  display: block !important; // !important required to override inline style
}