Tried it with wp 4.3.1 and woocommerce 2.4.8 and it works perfect.
This plugin adds custom field search to woocommerce search. SKU and user custom fields results are listed as well as content and title searches.
Great!

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Plugin para realizar búsquedas por campos personalizados incluyendo SKU (número de referencia) o cualquier campo personalziado creado por el usuario en Woocommerce.
Funciona a la perfección a pesar de llevar 2 años sin actualizarse.

nice plugin, to make it work fine with WPML i replaced the current code

$posts[] = get_post($product_id->post_id);

with this one:

$langInfo = apply_filters( 'wpml_post_language_details', NULL, $product_id->post_id );
		if(ICL_LANGUAGE_CODE == $langInfo['language_code']){
			$posts[] = get_post($product_id->post_id);
		}