It does actually sound like they are getting stock when available, and that points to liquidation as Jimmy has mentioned, so why not head to the liquidation sites and try to cut out their margin.
Now you are going to want to know any decent liquidation sites, RIGHT. Sorry, but I have no idea myself. I spent a little time looking for surf brand products through liquidations smyself, but gave up early on in the piece.
I guess you just have to keep a constant eye open, and joing a few mailing lists is also a good idea.