http://www.e-techsiliconvalley.com/store/index.php?main_page=product_info&products_id=14507

I’m pretty sure that this is about the same as what you are looking for. It is the same specs: 9v dc and 500ma, and it has the 1/8″ plug, so i think it should work. I have an older holy grail as well and the power supply on mine died for the second time, so i have been looking for a replacement.