shadow,
we ran into the same situation in BOS once and ended up booking through a Bed & Breakfast agency. It was a nice house in the Back Bay area and we were the only guests. Not bad for a couple of nights.
Here are a couple of links.
http://www.boston-bnbagency.com/site...ston/home.html
http://www.homesofboston.com/herbsthaus.htm
http://www.unionparkguesthouse.com/

Don't know if you even like to stay at B&Bs, I don't, but perhaps that may be your only reasonable price choice. Good luck.