...........but the NFC radiation is messing with your head?
I've got this pack of three for a tenner off Amazon and they work finehttps://www.amazon.co.uk/gp/product/B00QIEX04K/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
An empty Quavers packet does the trick if you can stand the smell