Do a search with "roof rack" and you will find several threads. If you just need bikes, the thule 889 rack pack provides a good solution by adding one load bar to the factory rack (cr started the thread which includes pics). I just purchased the 889. I think there also was a possibility with a Thule VWadapt kit.
If you can wait until summer, it is possible that the Pilot (a bit more flexible and more standard) racks may fit the MDX but no one seems to know for sure.
A few members have installed Yakima tracks on the MDX, which is a more flexible solution but is a bit more complicated. Good luck.