All of the bottles ive acquired from the 90's came from different sources in belgium. Some claiming to be locals in/around Soy, some claiming to be friends of Dany and most of the time its random people contacting me saying "they know a guy who knows a guy." Sometimes its on here, on BA, on RB and even facebook.
What the people want in return varies quite a bit. Not surprisingly, the more times these bottles change hands the more people want for them. I acquired some 1:1 for armand seasonals. Some I got with no details exchanged just "give me what you want in return."