I'd keep trying priceline and see what comes up. If you're bidding 4*, keep in mind that you can leverage the 3*-max zones to do a lot of free rebidding. Also check travelzoo now and then, although I doubt if anything <$200 will come up for October.
Meanwhile, the Crowne Plaza at LGA has a free shuttle to the subway and I see fully cancellable rates on October 18 of $152. It's certainly not ideal, but might make sense to book now as a backup in case you can't find anything in Manhattan that meets your budget.