Common wireless gadget with rotary encoder to connect with Arduino
That sounds like a candidate for building your own.  It shouldn't be too hard.

There's plenty of low-cost Arduino-compatible wireless modules available.  My choice for this would probably be the nRF24L01 - dirt cheap, reasonable range, well supported.

Attach that to an Arduino Mini or Arduino Nano (for instance) and connect a rotary encoder of your choice.  Write the sketch.

Add another nRF24L01 to your main Arduino to receive whatever you send.

Due to the way the nRF24L01 works you could quite easily have a number of remote modules talking to the Arduino through the same channel.  I'm sure you could think of other things you could do with that wireless channel :)