You will struggle to be honest.
But, one way round it if you dont know anyone and do not want to pay prices outside the ground, is to get them to register as a One United member and apply for tickets, not guarenteed but a cheaper option as tickets for United v City will be going for well over £100 atleast,,,,,,, ive even paid £200 for a united v city ticket afew years ago.
Or ask me closer to the time and i may be able to help you out,
Chris