It won’t be easy finding someone to teach you a Cockney [traditional London working class] accent. Fewer people speak with the ‘full-on’ accent nowadays, and if they did, they would probably not be using Italki to learn foreign languages.
Having said this, if you search YouTube for well known [or less well known] English actors and performers, you can try to copy them. You could try ‘Bob Hoskins’. He ‘starred’ in a series of TV adverts for BT [British Telecom] in the 1990s. The London accent has moderated in recent decades and has moved away from traditional Cockney. For an ‘attenuated’ version you could listen to Michael Caine or Timothy Spall. It’s quite difficult to develop an authentic Cockney accent, as the American actor *D van D discovered when he took a part in the children’s musical Mary Poppins.