SMART ATO Regular Check Valve

I see that the Micro comes with a Siphon Break / Check Valve with the purchase of the Smart ATO Micro. I bought the Smart ATO Regular size, and it did not come with a siphon break / check valve. I need one as my Smart ATO naturally siphons water into my sump after it pumps the desired water to reach the appropriate water level. The pump inside my reservoir is lower than hose output that's in my sump. I thought this would assure that the water would not naturally siphon, but even with my device set up correctly; it still is naturally siphoning (intermittently).

Can I buy the siphon break / check valve that comes with the Smart ATO? If not, is there one you'd recommend?