I have a 2225 and am adding graticule lighting. It never came with it.
I'll likely go with LEDs, and use the +5.2V supply (non-critical digital logic) with an appropriate current limiting resistor.
You can still find these original parts online:
The plastic graticule reflector is Tek part # 378-0877-02, and is used on the Tek 2232 scope. It's just the plastic piece with white reflective tape along one edge. You could add two diffused LEDs, or regular bulbs. Note there are only two holes for lights, and the center portion is a screw hole for mounting.
The illumination board and reflector assembly with bulbs is Tek # 671-1463-00 or 671-0795-00. This has the plastic piece above, the PCB with two bulbs, and the wire and a connector. Not sure of the voltage it uses, but they are wired in series.
You may want to add a brightness adjust knob on the rear of the scope.