I'm trying to get the sku number for a product Variationuct varient

In template-functions.php
The mp_buy_button function.
on line1753 i need to output the sku number for each variation in the dropdown list.

Any idea's how to do that?

$variation_select = '<select class="mp_product_variations" name="variation">';
foreach ($meta["mp_price"] as $key => $value) {
$disabled = (in_array($key, $no_inventory)) ? ' disabled="disabled"' : '';
$variation_select .= '<option value="' . $key . '"' . $disabled . '>' . esc_html($meta["mp_var_name"][$key]) . ' - ' .$sku[$key]. ' - ';
if ($meta["mp_is_sale"] && $meta["mp_sale_price"][$key]) {
$variation_select .= $mp->format_currency('', $meta["mp_sale_price"][$key]);
} else {
$variation_select .= $mp->format_currency('', $value);
}
$variation_select .= "</option>\n";
}
$variation_select .= "</select> \n";