New S Class owner, i am always loved the look of the AMG spoiler. Looking into purchasing one. Here are some options i came across on Carid.
T5iŽ - Factory Style Rear Lip Spoiler


These come with a paint option also. , They use a 3M tape with a Note to add silicone adhesive. See added Instructions. Have any members used such products and how did it work out for you. Thanks, any advice is welcome.
Price point is $315.00


T5iŽ - Factory Style Rear Roofline Spoiler $284.47 This one not sure on, looks kinda goofy if you ask me on some cars.

 

I have no experience with the site you have mentioned, if you want to keep things more OEM styled, I can recommend Jbspeed.

https://www.jbspeed.com/w222/

 

I used carid for Rims and tires before, customer service was good, however shipping and Time to door not so much. I will check out Jbspeed.com ( update) I will pull the trigger with JBspeed looks like it will save money and the customer feed back looks well, thanks Vincheung!

 

Check eBay, plenty of rear spoilers already painted, good quality, this is where I've bought mine, very happy with it.