987 Boxster transmission swap options

[j2m304]

Hi guys,
I just bought a 2008 Boxster from a family member that came with a "noise" in the transmission. Spoke with a mechanic friend who specializes in euro cars and he said the input shaft / pinion gear is worn - said that it's easier to just swap in a used 5 speed from a 986, or keep an eye out for a front end damaged boxster and swap in a different transmission.
The noise occurs at anything over 80km/h (50mph) and could be described as a bit of a howl when moving the transmission from a loaded / unloaded state at speed. Pushing the clutch in stops the sound as the trans is then fully unloaded. It's easy to replicate, and can't be heard with the top down as the wind mutes the sound.
You can't "feel" the sound either.

I've read a few posts that indicated an Audi A4 transmission is compatible with the 986, and was curious about what would be compatible for the 2008 987 2.7L 5 speed transmission. Any advice for compatible parts / anyone selling a working 5 speed (preferably in Ontario, Canada)?