I'm not that familiar with off site hotels that are in that price range, particularly in December. While the early part of the month is low season, many people go to see all the holiday decorations that are put up around Thanksgiving.
Your best bet would be to go to
www.disboards.com and review the off-site hotel forum there. You can also check
www.mousesavers.com. They sometimes offer discounted hotels for readers of the site.
My opinion is that it will be on the difficult side to find something that is close to Disney AND around $80 per night. Perhaps priceline would work.