PPL Has Auto Drain Kits. The kit is a motor assembly as noted above, not a complete powered valve assembly. Description says it fits Valterra and Bristol valves. I like the idea of the valve and motor being separate components, can replace one without the other. Still, at the price I think I'd go with new cable-equipped Valterra valves. They're about $50 on Amazon. A little more for 3" and a little less for 1-1/2".
We have those Valterra valves (72" cables), and they're 12 years old, stiff but still working.
