I have heard the floating alarms are annoying, but we don't have little kids, so it should be okay!
The Techko S187D, is out of stock on Amazon, but Amazon Warehouse has a couple of used ones. Just need to click other buying options. Not sure if delivery would be fast enough now.
The Lowes at 54/41 also has a bunch in store, but they want $32 each which is crazy.. I think Lowes might price match Amazon though?