Here you go:
XM satellite radio antenna with pink fakra, Magnetic, Delphi 999U9-VS000
It's got a rubberized base with some adhesive on it (haven't removed the adhesive cover). I've got a relatively strong puck magnet under the cover and it's wedged behind the seat cushion as well. I have not noticed it moving around or scratching my custom painted cover. I never ride the bike without the top box so mounting it somewhere when the top box isn't in place isn't an issue for me. It's just a matter of being able to remove the top box for maintenance should I want to or to bring it inside at an overnight stop that I was concerned with it not being permanently mounted. In those cases, I'd simply store it under the seat until the top box was back in place.
I guess I've been fortunate that my cars have never had any significant dropouts (at least nothing like the bike). I'm sure that's related to the relatively flat area I live in.
Antonio, I reached out to old-timers personally and heard from Matjaz last night. He informed me he is away from home until December 16 (16/12/19) and unable to login to this site. I expect you will receive a response from him upon his return. In the past when away from home his response time has been long. I hope this information is helpful.