Di2 10 speed

Well what a mornin!!!

Got 2 miles into this mornings ride and my rear mech breaks from the hanger and wraps around the xhain, wheel etc!!!

New chain and hanger are needed not sure where to get the latter from) but unfortunately the rear mech is well..... Knackered!!!

I'm struggling to find a 10 speed di2 ultegra mech. Can I change to 11 speed or does that mean a whole new group set upgrade!I