i use http://www.travelcusehotels.com. the site is an aggregator affiliated with hotels. com which means it searches other sites and presents you with the best deals available. good luck and hope this helps!
What is tripping you up is the combination of a high rise room and a maximum $150 per day price point on a weekend during tourist season in NFO. Since most hotels there raise their weekend prices up to twice as much as during the week, you're asking for a lot. Either you have to drop the high rise expectation or raise your price level. You won't find much if you keep both, especially if you want that high rise to give you a falls view.
I assume that you've already checked prices at places like Travelocity and Expedia. Other than for a couple of smaller high rises on or near Lundy's Lane, nothing fits all of that criteria. If it were me, I would drop the high rise demand as there are plenty of decent hotels in your price range with 2-3 floors.
Both the Comfort Inn and Quality Inn on Clifton Hill are great hotels right on the smae street everything is happening. They are cheap.
Your our traveling by train so I am assuming you dont have an automobile. There are many and I mean many smalelr hotel, budget type hotels throughout Niagra Falls. You defenitly can find what your looking for the only question would be quality. The farther away from the falls the cheaper it gets. You can still be within walking distance though. My suggestion would be to either search aorund on some web sites. niagra Falls.com or travelosity before hand. Also tripadvisor is great and has pictures and reviews on all the hotels, motels,,,etc...
Or if you just have some extra time when you arrive you will be able to walk and find one. At the smaller hotels and motels check the room out first there are some lousy rooms so dont get fooled.