Fortunately, this seems to be a very rare thing to be booked for (the lights thing) and noty too much to worry about. making up a temporary plate that is easy to see will get you away with it for the great majority of highway patrol, especially if carrying bikes is a one off occurrence for you (eg interstate, new towbar, new bike carrier, new car etc). fine is $489 last time I was chatted for it.
you can always simply remove your existing plate and either bolt or zip tie it to your carrier/bike - if thats going to be difficult, then white paper printed black and white large numbers, laminate it, install, then be prepared with a story about ignorance of law, you never carry bikes on this car, normal car is in for repairs and we have a number plate for that one etc etc