There is the little finger that pokes away from the brake booster that is what I call the ECM bracket, It is just behind the booster and is held with the studs off the booster, the booster must be removed to replace this.
Then there is the plastic retainer that the ECM lays in this slides onto the bracket and that's what holds it in place, the ECM then lays down on that and has the 2 nuts securing it to the retainer.
What one did you break?
The plastic part is available but the pot metal bracket that sits behind the booster is ZR-1 specific and I have a spare if you need one just let me know.
I also have the plastic one..