When I had to leave my car for the 72 hrs, I arranged a deal with the owner directly (the day or night staff don't have authority to do this) at:
Super 8 Motel - Niagara Falls/Buffalo Area
7680 Niagara Falls Blvd
76 Street Niagara Falls Blvd
Niagara Falls, NY, 14304 US
Phone: 716-283-3151
Fax: 716-215-0296
Lots of parking in the back, well lit, security camera, but not the best part of town obviously.
$ 20.00 cash for 4 nights
The handy part about it is if you have to go back to canada in the meantime, there is the shopping shuttle nearby at fashion outlets.
The I-190 is only 2 minutes away and is a very quick drive up to Lewiston.