Yes, that's the way they work, and yes those ones are always tricky to get & replace with anything but originals, so many dimensions to get right.
I found spare antennas for the seemingly identical Maycom AR-108 on eBay and contacted the seller but he had no buttons.
I have some old oscilloscope (or whatever) buttons that I might be able to turn down on a lathe, if they otherwise "fits".
But I'd be grateful if you would have a quick look through your bits & pieces. It's for a pilot friend of mine.