Chance wore a light grey Champion Heritage All Over Script shirt for his headlining Lollapalooza set. While that color way is not currently available, the olive version is currently available for pre-order here. You should snag it now, since some sizes are already sold out.
For a similar look, check out this Big C shirt.
Chance also wore his signature hat and Gucci belt.
UPDATE: Shirt now available in white here!