3.25 x 10 Wall Vent Modified

I am having new kitchen cabinets put in on the main floor of a two-story townhouse with a shared wall on the kitchen side. The current layout requires moving the 3.25 x 10 wall vent four inches to the left to meet a 4" fire code separation requirement between the stove and the refrigerator (fire safety issue with stove being next to a vertical surface.) An OTR 400 CFM microwave will be installed which will need to use the 3.25 x 10 vent.

Is it possible to create a modified duct piece that would attach to the existing duct which would then allow me to move the opening over four inches? I can easily cut the sheetrock away and fix.

I'm imagining something that angles from the top down to the left to help keep the opening as large as the original, while the right side would run vertical, and would close off four inches to the right. The left side of the current duct would be cut out so that the new piece could attach. Studs on the first floor are not an issue. Duct runs through second floor walls and into attic where it is attached to a round pipe which then vents up through the roof.

Are there any other solutions that would work?

 

Here's an image of the vent. Just wondering what I can do to modify the existing vent so that I move the opening 4" to the left. Can't move it above the ceiling as it is running through the wall and up through another floor and into the attic vent.

 

A sheet metal shop or HVAC house could fabricate an offset for you.

Or you might be able to modify a couple of flat angles to serve as an offset: