Here comes four scales that I like very much. Elas so mixolidium, mixo with 6th minor, mixo with +4 and mixo with 6th minor and 9th minor, also know as Phrigium major. All this scales works on major with 7th chords. There's also a pentatonic for each one. Try to play it over a A7 chord, starting the scale on the 5th fret.