Try ebay, I have paired four different Roku 3 remotes to 3500 stick. Look for the RC03 remote. This remote has headphone jack, that WILL NOT work on the 3500, but the rest of keys will. If your tv has cec feature and it's turned on, the volume keys originally used for the headphone jack, might control your tv volume.
None of the current remotes will work with your 3500 stick.
Edmund
Roku Community Streaming Expert
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