Hi @Anonymous User
You can buy a replacement nowtv remote controller for your black nowtv box from the Sky Store Accessorises Shop.
More info here
https://accessories.sky.com/catalogue/now-tv/all
Alternatively look at a replacement nowtv box that you can pick up from Curry's with a bundled voucher pass for £10.
If you haven't factory reset your box and still have your existing account details on the box, then maybe consider the free Roku remote controller App that you can download for free from your mobile phone / tablet Apps Store.
