I've scoured the internet for this part. No exploded parts drawings list or depict it. It connects the rail on the glazing to the frame. It's pretty worn out and much of the plastic has cracked and chipped away. I have ordered part 54 10 7 039 734. It is not this part. Detail: Inside view: Other side for comparison: Parts Drawing (it is not part #14 or #15; I have #15 in my hand):
I had no idea any parts were available for the sunroof. My thought was the whole thing would need to be replaced. Maybe you can find a friendly parts guy at the dealer who could search that part out for you. I hope you can find it. Keep us in the loop & let us know how it goes. Welcome to M/A
Well I went to realoem.com but it did not have any more info. I would try giving https://www.allmagautoparts.com/collections/mini-cooper or https://www.outmotoring.com/ a call. Both are great venders and very helpful. Sorry I am no more help
Almeg has this, I know it is a little more than you want. https://www.allmagautoparts.com/collections/mini-cooper/products/02-03-04-05-06-mini-cooper-sunroof-glass-roof-assembly-54107053424-r50-r53