The standard phone/GPS holder clip that came on my 2018 Countryman won't expand large enough to hold either my Galaxy 8 phone, or Garmin. It appears to only hold an I-phone. I've looked around to find a more expandable clip that snaps on to the existing stalk in the car with no luck. I can only find complete phone holders that snap into vents or attach to the dash. I don't want another entire phone holder. I'd prefer to buy just the phone/GPS attachment clip. Any suggestions/ideas?

Not sure how it attach to your mount, but I have the CravenSpeed mount and it fits the Garmin and I'm very happy with it. It attaches behind via a tiny bolt and nut. Might check them out to see if this is a possible option.

https://www.cravenspeed.com/smartphone-fixie-for-mini/

Cravenspeed Gemini and a Samsung Galaxy S8 installed in my a '19 Countryman SE....

Thanks...i'll check it out.

My Galaxy 9 standard with case fits in my '18's holder/charger. An 8 should fit unless it's a + size or has a huge case.

OK Thanks. For some reason, neither my Galaxy 8, nor my Garmin fits.

That's surprising to hear! If you picked up the clip style like @BossHoss and it's still not fitting, you might want to try the magnet option!
I've PM'd you.