The transfer period is over, but there are still opportunities. There many good players without a club.Some names of them are big and I think that someone of them will still find a club.

Serge Aurier - Been very successful with Paris Saint-German.
Franck Ribéry - Everyone knows him
Marko Marin - 2019 Player of the year in Serbisch
Jack Wilshere - 182 games in the Premier League
Shkodran Mustafi - World Cup Winner 2014

Source: https://www.transfermarkt.com/statistik/vertragslosespieler