I located the supplier in Alberta and saw that Lowe's were their local distributor. A trip to Lowe's however confirmed the worst. Those pieces were only sold to the trade.... Then Andrew (from the plumbing department at Lowe's) put me in touch with Chris who was apprenticing as a Tin Knocker with a local builder and I finally got the work done...
Chris spent close to 3 hours yesterday and gave me exactly what I wanted.
Next step will be to frame in the alcove for the washer and dryer, complete the plumbing and finish the electrics.
Before: The ducts were almost 8 inches away from the bottom of the stairs
After: A new 90 degree elbow and the existing 45's take the ducting close to the stairs.