Sorry but none of the current remotes will work with purple Stick. You try ebay for used Roku 3 remotes like RC03. The headphone jack on that remote won't work with 3500 stick. But if you have more current TV with cec feature, the volume keys on RC03 remote might work your tv's volume.
I don't think its worth it buying used remote for such an old Roku model. I would go with a new Roku device like the following:
Amazon.com: Roku Express 4K+ | Roku Streaming Device 4K/HDR, Roku Voice Remote, Free & Live TV : Ele...
Edmund
Roku Community Streaming Expert
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