Rob,

I got lucky and bought a piece of 3" polished aluminum tube from a rice shop in Whitby for $10. It was a section that had been cut from a CAI.

If all you want is a straight section of tube to mount a filter to your turbo, try one of the following places:

Metal Supermarkets (look it up on http://www.canada411.com) or
http://www.lorenz-son.com/

For what you want it should not cost more than $10 to $15.

Good luck!