I think the best price is eBay 5 bottles for $32 shipped. http://www.ebay.com/itm/5-ZDDP-MAXX...Parts_Accessories&vxp=mtr&hash=item3f11c0d520
Or if there's a local parts store and ask if they have Valvoline VR1 Racing Oil. It can be used for daily driving and it already has the ZDDP additives in it.