How to fix placement of over-stove exhaust
The best possible idea is to find a good sheet metal place and have them build you something beautiful and custom. It wouldn't be cheap, but shouldn't be outrageous, unless they have to come and visit (which they shouldn't, if you can make a good drawing).

Alternately, get about double the amount of tin ducting that would ordinarily go into such a project and start hacking away with abandon. Use good metal tape (not duct tape -- eww!), screws where appropriate, and wear gloves. Then -- and this is where I give away all my trade secrets -- hide that mess with a 3 sided box made out of plywood or something nice you've got lying around.