Sorry, my mistake, my overflow is actually 1 inch.
Are you using all rigid pipes like mine? If yes, you should require:
1.) a check valve to prevent back flow if your outlet to the DT is below the water level. Otherwise you'll have a mess if you turn the return pump off,
2.) a regulating valve so if you get a bigger pump you can still adjust the flow to match the overflow rate,
3.) a union or 2 depending on your pipe design for dismantling and maintenance if necessary.
My pump is order online from China so I doubt you can find it here.
One draw back of using a submersible pump is the heat generated by it. I'm using it b'coz I cannot find a external pump small enough for my use. So if you happen to use a slightly bigger pump, you should increase the size of the overflow to 1 and half inch.
Above is just my opinion. You study and improve on it further.