Minor chords can easily be altered to form minor 7ths. Here are the shapes for the E form (root 6) and A form (root 5) minor bar chords and minor 7th bar chords.
Fm
Fm7
A#m or Bbm
X A#m7 or Bb m7
Here is an example which makes use of these chord forms. They are all played at the 8th fret. The Cm and Cm7 are played as E form chords, and the Fm and Fm7 are played as A form chords. The G7 is a C form.