Joshiko, I've found that reloading the game (a pain) a few times will change the list of transfer players. They may be uncommon, but they're out there. Acquiring new players is a game of patience. And I'm only 2 levels ahead of you at most.
Nico, keep relisting them at full value. They'll be bought.
Just keep upgrading your team as best as you can - I have 10 players on my squad now who weren't there on day one of this season. I'll probably pick up 5 or 6 in the first week of next season too - though it's a hard time to get them with everyone scrambling for new players.