GO Transit F7B Exhaust stack

Hi guys, I will be building the GO transit F7B hep unit pictured bellow, does anyone know who makes this type of exhaust stack for HO scale.

I have no idea what that thing is, but the F7B normally has two exhaust stacks between the 36" roof fans.

Here is more info on that unit in your photo.

http://transit.toronto.on.ca/gotransit/2506.shtml

I suspect that it is a new air intake and or exhaust for the 900hp “APU”

APU Unit 800, made from a cabless F7B, is positioned between the lead locomotive and the rest of the train in order to provide Head End power. Photo donated from the Daniel Garcia collection.

does anyone have better images of this unit, thanks.