Thanks for the info Al.
My shocks are old and have many miles, and even though they still do their job, I know by experience, that having brand new aftermarket shocks changes the bikes' behavior incredibly.
I'm not a big fan of BMW shock refurbishing. I had a pretty bad experience with this option when I had a K100RS. I went that route and it ended with the bike being unusable for months added to the fact, that I could have had a major failure while riding (fortunately, it happened with the bike stopped).
So, to make my search more precise, I'm looking for low miles aftermarket : Wilbers, WP, Hyperpro, EMC,....
If I don't find good used ones, I'll bit the bullet and buy new ones.