On Amazon I bought a set of Chinese-made Macro Extension tubes for the Canon 6D. Leitz quality they are not, but then they are not hundreds of pounds/dollars either. They do the job adequately it seems, and have the electronics built in for auto focus etc., although I find with some shots it is as well to switch to manual. They arrived this afternoon, so forgive me if I am playing with ny new toy for a few days!
www.amazon.co.uk/gp/product/B00E9M33PY/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1