You have to get it touch with Roku Tv manufacturer, Roku only supplies the UI for the Roku tv. Anyways the tv is 5 years old, way out of warranty, just buy a cheap universal like the One-For-All urc-7935 streamer remote:

Here it next to Roku tv remote, it can be found cheap on ebay for an open box version:
urc-7935 remote | eBay
Edmund
Roku Community Streaming Expert
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