In need of some check valves for 1/2" ID hose - GVRD or Online

[gregzz4]

Any idea where to get a couple of these, either locally, or online ?
They must fit 1/2" ID vinyl hose ...
Not looking for 1/2" check valves for PVC

I'd like to install them on my GFO and Carbon reactors to stop product from back-siphoning into my sump when the pumps are turned off

Thanks for your help