I have a used 42cm wide Specialized S-Works handlebar that is probably best for use as a stoker handlebar. ( I can and will explain if anyone is interested; this would best be done in a separate email. )
They weigh 175 grams on my digital scale.
I am interested in selling them for cheap.
If you ever wanted to try 42cm handlebars for the stoker, this might be a good way to try this width bar.
Contact me with your email address if you want to hear more about these handlebars.