I went a slightly different direction with my Creature mod, I used standard 555 bulbs and sockets, but instead of wiring them into the GI, I wired each one into one of the lightning bolts, ran the wires right onto the board. This way you get the best of both worlds, the lights don't stay on all the time, but flash the same way the lightning bolts do, you even get a bit of a pattern when in attract mode!! I also used LED's so they should last a long time and don't draw much more current.
Dale