I was annoyed, too, when they took away my sushi mat, but I really don't think it's a problem in-game any more.
The sushi mat is 50 sand dollars and the Mer-kin stashbox gives 30-50 sand dollars, so simply running the sea quest almost pays you back, even if you don't find any sand dollars or thingpouches containing sand dollars along the way. I always eat sushi when I'm doing the sea - and I end up with plenty of turns of Fishy for doing so - and I always end up with more sand dollars than I started.
(And if I have 40 or so turns left after I am done with the quest, I buy the skate park map, drive off both kinds of skates, and farm for 30 turns with the 3 skate park buffs, yielding 30 more sand dollars, for a net gain of 5.)