Wye checks are the best type you can buy.
A hole in your return line is not a bad idea but you typically will still have some back washing, especially if your siphon brake holes are slightly clogged (or worse, completely clogged).
Although it is not a good situation to be in, if your very limited on how much water can back flush into your sump, a wye check valve will almost instantly stop water from back flowing. I've got many of these in operation and they work!
The flap type valves are notorious for failing and most of them restrict water flow.
If you want to try a flap type anyway, Lowes sells them
Joel