Dave, get yourself a couple of 8mm compression fittings and machine off the threads, leave a small spigot on one end and a matching recess on the other to help locate them while silver soldering. Add any bits to the ends as needed.
This is one that has been modified

Some of the other parts

Soldered up in the foreground

Another option is a piecing saw and stick of solder, saw a series of holes that go almost all the way through then you can bend the now flexible pipe and solder back up which fills the saw slots. Not sure if you can see all the slots in thsi exhaust pipe

Last option put the job out to a man who can