Roku stick's like the 3600 only respond to wifi roku remotes. A replacemebt remote would cost $20 or more. That model isn't worth spending that much on replacement remote when you can get the latest roku on sale for $30, the express 4k+:
And if you were to lose the express 4k+ remote you can still control it with cheap universal remote since it responds to IR commands as well.
If you want just a replacement remote for the 3600 you can buy it from amazon:
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