As it turns out, a pure white bikini is available for all collab characters since they don't have a team bikini to default into during top-bottom outfit editing in the changing room.
I didn't need to buy that 3 dollar swimsuit but I guess I just paid for some extra colors, oh well.
https://x.com/1ku8MZH399A3I0t/status/1947968723601809734/video/2