Usual suspects: Eder Alvarez Balanta*, Luke Shaw, Ben Davies
Emre Can with a bit of positional training - should still be young enough. Same goes for Diego Polenta.
Vurnon Anita, Bruno Martins Indi or Stefano Denswil if you need homegrown Dutch.
Georgy Schennikov or Ruben Duarte depending on how they have developed.
Samuel Umtiti, Mapou Yanga-Mbiwa, Aymen Abdennour or Angelo Ogbonna are more Central Defenders who are comfortable on left.
Bit less expensive: Sebastien Bassong, Alvaro Dominguez or Samir (if still at Flamengo v. cheap).
I've played with many but not all of the above but think they could all do a job both domestically and in Champion's League. Obviously splashing the cash on Luke Shaw (not even sure £26M will get him) will get you a better player than £5M will but, unless the rest of your squad is uber-awsome, £26M is a lot to spend on a LB.
*Anyone (including me) who mentions Balanta should have their fingers ritually chiseled off.