If it was me with this problem. I would probably buy a very cheap scope (99%+ of the audience would never notice it is out of place in a professional lab), brand new or a cheap one on ebay in clean condition, and shown to show pictures on the screen.
Then modify the soft on/off button, to switch on automatically, and try to create a simple button sequence or freq generator, to show something on the screen after it turns on.
E.g. Wire/cheap probe between probe cal and input(s), with soft turn on button and auto buttons, pressed via a 556 timer, on after 5 sec and autoset after 15 sec or something.
Or when buying an older (modern looking) cheap scope on ebay, find one with a physical/real on off button.
I can't see why you are bothered by losing the guarantee, because by the sound of it, it will get so roughly treated during filming and transportation etc, it will soon be in too bad a shape to easily claim under the guarantee.
Cheap ebay low frequency scopes, but made by quality manufacture's, may be more physically robust than cheap brand name ones. But I'm speculating here, and could be wrong.
Also steer clear of any with auto power off (but you might be able to disable it in the menus), which I have read about.