the little cheepo 12v to USB 5v cigarette lighter plug for a car works for this pretty good. the pushbutton ON, slow blink, fast blink, OFF function of the 3v box gets about destroyed when hooked to 9v a little while so it'll stay on all the time when power is fed to it.. slight risk(?) but not too spendy if it gets cooked wrong for trying it, worked fine here tho 1st try.

next thing I learned is EL wire runs low current AC, about 100v at 1000hz, can bleed some noise right into a pinball machines electronics if its too close to stuff that'll pick it up.. 1khz hum possibly trigger other things too, especially if the inverter and EL wire arent solidly connected to each other, wire to EL connection (shrink wrapped) or the connecting plug itself.

you might be ok with straight tapping into the 6-7v GI lighting circuit with a good sized diode or two, they'll usually drop about .7v and half wave rectify at the same time. the higher the voltage the louder the potential 1khz noise too btw, and if voltage or current are really too high, the EL wire is going to want to start heating up for it. what you have sounds like the same I picked up 5 of em arrived couple weeks ago, looks pretty cool in my zizzle (toy!) machine but had to re-route all the machines ribbons up the center underside of pf 6" away from the EL stuff on the left, also put shielding (sheetmetal) between the underside of the pf and the little zizzle mainboard. idk how sensitive a full size pinball machine might be but know people are doing pretty cool stuff with the EL wire.

it might be easier-safer to go with small 12v LED strip lights and underfeed em the 6-7v? know it just wouldnt look quite the same as the EL stuff, can always fall back to the LED strips if the EL wire causes issues.