Rear derailluer broken bolt I am trying to figure out the right part to replace this bolt that broke.  It went through the rear frame of bike into derailleur to a shimano dyna sys II unit.  I believe it is a hanger bolt but the ones I find online don't look exactly like it as it has a smooth portion (where the break is) that I don't see on the online.  Please see attached photoS and help.  So lost.  

Thanks
This looks like the Syntace 142 mm X-12 axis bolt that also serves as the derailleur hanger. 

See https://www.pinkbike.com/news/syntace-142mm-12-norco-2011.html

Syntace catalogue (there are several lengths):
https://www.syntace.com/en_GB/products/liteville/accessories-spare-parts/630/x-12-screw-for-derailleur-hanger-28.5mm


Photo Syntace

In shops (be sure to buy the right length):
https://www.bike-components.de/en/Syntace/X-12-Derailleur-Hanger-Bolt-p24466/
https://www.bike-discount.de/en/buy/syntace-x-12-screw-for-derailleur-hanger-28.5mm-44555