Try these but I don't know how reliable they are http://www.ebay.co.uk/itm/2200mAh-Portable-External-Power-Pack-Backup-Battery-Charger-Case-For-iPhone-5-5S/171055625408?_trksid=p5197.m1992&_trkparms=aid%3D111000%26algo%3DREC.CURRENT%26ao%3D1%26asc%3D14%26meid%3D8306284538492286248%26pid%3D100015%26prg%3D1006%26rk%3D1%26sd%3D171055625408%26 http://www.ebay.co.uk/itm/BRAND-NEW-TDS-POWER-PACK-FOR-IPHONE-5-IN-BLACK-4200MAH-EXTENDED-BATTERY-LIFE-/360634066956?pt=LH_DefaultDomain_3&hash=item53f777280c