I don’t have resources for Hawai’i, but my family has used Parrish for decades for many different places on Kauai and they’re excellent.
I would note that many rental properties will open up bookings 12 months (occasionally 13 months) to the day for the next year. And for anything around a holiday, be prepared to book immediately in the morning, precisely when it opens. (And once you have that booked, book your rental car as well.)
Many places may also have a standing reservation for the Christmas-New Years period; ask in advance so you don’t get your heart set on a place and then discover that they rent to the same family (or use it themselves) annually.