Is this a T1N (up to 2006), NCV3 (2007-2018) or VS30 (current)?
MB / Freightliner will happily sell you a pre-cut blade that goes into the T1N flip key for about $60 (to who knows what).
The T1N blade is held in place by a "roll pin" that is visible if you flip it out half-way and look at the side near the pivot.
You just push out that pin, remove broken bit, insert new blade, push pin back in.
I can only assume the NCV3 and VS30 work kind'a the same way.
--dick