I agree Chadwick’s is a good source of inexpensive clothing but in the
past I have had mixed results with them.
will you be wearing a cap & gown? If so, then what you wear on your
body isn’t so important, since it will be covered up! Focus on some
nice makeup, something natural looking.
If you do need a dress, sounds like something like an A-line dress or
other belly-hiding outfit would work.
When I graduated from grad school, I wore the same dress I wore when I
graduated as an undergraduate, a sleeveless 100% cotton tank dress.
Hides any belly, went down to my ankles, didn’t overheat me in the cap/
gown, and I can dress it up or down. 20 years after graduating from
college I still wear it!!!
Good luck!
Stephanie