Does something like this exist?

[Kane Knight]

Or will I have to jury-rig something?

I'm looking for a "pedal" effect to pan vocals/other effect left to right or right to left or whatever.

I'm sure it'd be easier thana lot of effects to build, but I'd rather put some money into something professional.

[Joeleosis]

http://www.musiciansfriend.com/srs7/sid=040407004454066127240233264739/g=guitar/s=effects/search/detail/base_pid/151306/

If you run two speakers and a mic through one of these, I imagine it'd do what you want it to do. I run microphones through guitar pedals all the time and it sounds just fine to me, no idea if they make one specifically for vocal frequencies... the human voice is within the range of the guitar as far as I know anyway.

[Joeleosis]

Now are you actually looking for something that will fade in and out from channel to channel? Or just a switch? Because I think this one just switches between two different outputs.