the clamp is a common exhaust clamp for vehicle/commercial truck exhaust systems. google something like "cummins exhaust clamp" and go through the images. that part should not have to be fabricated. they should also be fairly cheap.
i just built one of theese for my sons 15th birthday. me and my 11 yo found an indian made cricket bat in an antique shop and it was his idea to do the build for his brother. we just stripped the paint sanded and re stained the wood, a little ageing and i was done quick and dirty, not very sa...