Copy of the espresso_google_map_link() which uses HTTPS, place this in a custom functions plugin to override the default function.

ee_espresso_google_map_link.php

<?php //Please do not include the opening PHP tag if you already have one

function espresso_google_map_link($atts) {
    global $org_options;

    extract($atts);
    $address = "{$address}";
    $city = "{$city}";
    $state = "{$state}";
    $zip = "{$zip}";
    $country = "{$country}";
    $text = isset($text) ? "{$text}" : "";
    $type = isset($type) ? "{$type}" : "";
    $map_w = isset($map_w) ? "{$map_w}" : 400;
    $map_h = isset($map_h) ? "{$map_h}" : 400;
    $map_image_class = isset($map_image_class) ? "{$map_image_class}" : '';

    $gaddress = ($address != '' ? $address : '') . ($city != '' ? ',' . $city : '') . ($state != '' ? ',' . $state : '') . ($zip != '' ? ',' . $zip : '') . ($country != '' ? ',' . $country : '');

    $api_key = ! empty( $org_options['google_maps_api_key'] ) ? $org_options['google_maps_api_key'] : '';

    $api_key = apply_filters( 'filter_hook_espresso_google_map_api_key', $api_key );

    $google_map = htmlentities2('https://maps.google.com/maps?q=' . urlencode($gaddress));

    switch ($type) {
        case 'text':
        default:
            $text = $text == '' ? __('Map and Directions', 'event_espresso') : $text;
            break;

        case 'url':
            $text = $google_map;
            break;

        case 'map':
            $google_map_link = '<a href="' . $google_map . '" target="_blank">' . '<img id="venue_map_' . $id . '" ' . $map_image_class . ' src="' . htmlentities2('https://maps.googleapis.com/maps/api/staticmap?center=' . urlencode($gaddress) . '&amp;zoom=14&amp;size=' . $map_w . 'x' . $map_h . '&amp;markers=color:green|label:|' . urlencode($gaddress) . '&amp;sensor=false&amp;key=' . $api_key ) . '" /></a>';
            return $google_map_link;
    }

    $google_map_link = '<a href="' . $google_map . '" target="_blank">' . $text . '</a>';
    return $google_map_link;
}