Found this for you on eBay.
http://www.ebay.com/itm/Housing-Bac...e-Parts-For-HTC-M7-One-Dual-SIM-/161182059793
Pretty expensive for non original item without any markings or logos.
Thanks for your efforts
Look at lower edge of this cover at Ali Express. It does not look straight, lol.
I can't find on ebay