I finally got to finish this project today, so she's on the chopping block to make room for more.
Price? I don't know. I've never seen one of these for sale before. $100 shipped? EDIT: Now only $65 shipped.
SOLD on eBay
This was an Eclipse frame for an Autococker, but it's been modified to fit a classic Automag. The inside has been hollowed out a little to make room for the sear to move. A hole has been drilled in the top front to make room for the twist-lock assembly. I've added a trigger return spring and a custom-made safety, and I widened the back frame hole to accommodate the thumb screw. I'm also including a stainless steel main body screw that matches the frame, although if you're planning to put this on an RT or ULE automag, this screw won't work for that. You'll need one that's a tiny bit longer.
I will also include the sear extender thing that's in the video on the build thread. Sadly, it doesn't really change the weight of the trigger pull, though. It's mostly just something different and rare to show off to your friends. And you can use a normal sear instead, too. You just have more options than that.
Oh, and these grips are really nice. Near perfect condition. They even have copper washers installed between the screws and the rubber.
Two issues worth mentioning:
1. You will have to adjust your trigger rod to make this frame work. The rod you have is probably set too short, so you will need to back it out a little bit. This isn't hard to do, and I can walk you through it, but you really need the right tools (specifically, a bench vice and locking pliers). Otherwise you'll get frustrated very fast.
2. There is some marring on the top of the frame. This happened when I was hollowing out the inside, and the Dremel shaft rubbed against the frame. This is completely invisible when the frame is installed (it's hidden by the rail), but I thought I should point that out.