"dual brite" for post light

I like the idea of Heath-Zeniths 'Dual Brite' setup where the light is half power at night, but kicks to full power off a motion sensor.

I have a post light I don't want to change but I found an adapter that will make it 'Dual Brite.

I can't seem to find where to buy this adapter, though--

I don't know if I'm just Google-impaired this morning or if I'm missing something obvious-- but I'd appreciate a hand if someone knows where I can buy that adapter-- or if there is another similar product out there.

Thanks, Jim