Whoops. I completely missed that your image showed the RFDuino on the left. (I assumed it was just the layout for an MPU6050 breakout, and that you had pulled the image from a seller's site...) I also wasn't aware the RFDuino wasn't just yet another Arduino form-factor board, heh.
Seems straight forward to just put one on top of the other, possibly with double-sided foam tape, and then solder the resistors/wires where they're needed. I do this sort of thing commonly with
my own projects.
Not sure if you can directly put, e.g. a 1S Lipo powering the RFDuino. If you can't, one solution might be
this small board.
I'm not aware of a smaller MPU6050 breakout, unfortunately. But its .8" length seems like it shouldn't be too bad.