just a word of warning on this subject, there are a lots of sources of these items , but be carefull what you get or get fabricated.
A good friend of mine designs/fabricates exhaust systems and manifolds for high performance motor racing engines etc.
I asked him last year about making some of these items up, from the corse nest of vipers I got from baines.
End result was not going work out much cheaper than proper items, also their is more to making these things up than just welding and bending pipes to look the same.
If you take a good look at proper corse systems and how well they are made up, without loads of weld joins etc, also very carefully calculated pipe lenghs and bend angles etc to get spot on balance between both cylinders.
with a proper set carefully designed for the job you will get results, if not just some nice looking expensive pipwork.
you know what I'm saying guys.
Just my input .