Where to find vintage M7: in the last year I've seen it in out-of-the-way shopping mall fragrance shops. Recently purchased a new 50ml, vintage 2006, for around $45. The deals are still out there. Just have to be a relentless shopper to track them down. Of course, time is money, so if you don't want to spend lots of time (and money) shopping in obscure places, you might just spring for an expensive bottle online. In cost accounting terms, it probably works out to be about the same price in the long run.
In any case, it takes some time and money to get the good stuff. It is highly unlikely that the Avon lady will show up anytime soon with a well-priced bottle of vintage M7 that needs a good home.
To the BNers who've asked where to find it: best wishes for success with your search. Report back, let us know your thoughts when you've tracked it down. Money's on: you will love it.