I used a bit of leftover ply for mine.
Did two small plywood rails top and bottom with epoxy to engine box, and then a ply plate on top of the rails just the size of my ignition... (leaving a gap in the middle of the plate) Then a quick screw through the top and bottom plate into the engine box. Put one side of velcro on the plate, and the other side of velcro on the ignition (to act kinda like a shock absorber too!) And then a velcro strap around it all (through the gap created by using the plywood rails, and then the plate on top of the rails)

Good luck!

~Andrew