Good source for US Open Tennis tickets?

My wife and her friend have gone to the US Open the past few years, and were able to get stadium tickets after standing in line for several hours. They want to bypass that this year, so I’ve somehow been put in charge of getting tickets for them. Anyone know any good sources? I’ve been checking the standard sites - ticketmaster, stubhub, ticketliquidator, etc, but thought I’d ask if anyone knows any other good sites to try.

Do you know anybody who works for Chase? I believe their employees get some opportunities to purchase tickets.