If you're willing to pay for custom work, I have no doubt it's doable. I don't know that it's advisable though - exhaust length isn't typically arbitrary.
I haven't seen any off the shelf models that exit at that point (roughly adjacent to the mounting point of the mid pipe), but I can't claim encyclopedic knowledge of all ninjette exhaust options. I do recall seeing a pretty thorough list somewhere on this forum though. I'll see if I can find it. *EDIT* I was thinking of
this list, which is manufacturers for the 250. The 300 exhausts I've encountered are all a subset of this 33 company list. Some are certainly smaller than stock, but I wouldn't equate any to the 650.