i would feel awkward in the interim, but i would pay what i could now, and come back with the rest later. happened just the other day at the pot store. i came up $2 short and the guy was like “don’t worry about it” and proceeded to take it out of his tip jar. i died a little inside but he was really cool about it. a week later i came back in and gave him the $2 and tipped some extra on top of that for the kindness. he really appreciated it. i think that would have been completely acceptable here, too