Welcome!
...suggested that I get the official Apple adapter, which seemingly does not exist.
I doubt it exists as well. I can't remember 30-pin ever being an audio interface, becasue older iDevices all had a proper headphone jack. Apple and my other go-to source for odd stuff Apple does not offer, Other World Computing, show only charging cables.
I found the original manual for your Phillips device; it raised more questions than it answered. It shows support for only iPhone 3 and 4, and only a MP3 3.5mm input on the radio for external audio input.
It shows a double-ended 3.5mm stereo cable included with the radio. If you have a Lightning Apple device that does not have a headphone jack, that suggests to me that all you need is this $9 adapter that Apple still sells:
Lightning to 3.5 mm Headphone Jack Adapter
If your Apple device has a headphone jack and you still have the double-ended audio cable that came with the radio, I see no reason that would not work. If not, those are easy to find (Amazon link).
I remain a bit confused even after reading the manual. It would be easier for us to help if you post the Apple device and its exact sub-model to which you need to connect, and any extra hardware that lies between the two (hub, dock, etc).