There is a cheap ($120USD) Mid-pipe for a KTM 690 Duke on Ebay. Might be worth a gamble but from the pictures is lacks the feature that hold the graphite exhaust O-rings on. I have some time schedule with a local exhaust fabricator to make one but he’s a few weeks out from having time available.
On another note, I ordered a the Yoshimura Carbon Exhaust for the KTM 690 Duke. Yes it will bolt up but it sticks too far out from the swingarm so the cat-can pipe will need to be cut and shortened.