To see a wider selection of flights to Sapporo, try searching by city rather than by airport.
For flights to , Japan Airlines usually has the best prices. But it's best to go through your results thoroughly, to find the best option for you.
Accommodation is typically pricier at this time of year too. If you want to go at this time of year, try looking at other cities in Japan to get a cheaper flight.
Whoever you want to fly with, it's best to book your flights in advance, particularly if you want to fly on a specific date – otherwise they may sell out. Once you've booked, why not take a look at accommodation? Simply click on the ‘Hotel’ tab at the top of the page.