I understand what you mean.
Negotiate with higher level managers have higher chance to get the players .Sometime they just keep the player for nothing, an incoming offer will motivate them to sell.
I faced that problem too, my solution is to check the player stats, if they don't play on current season, I have higher chance to buy him.
One more tip, add friend to couple managers on higher level when you see them on Cup or Champion League, then you can check out their squads and their league opponent squads for good player.