Yes, the Shooter's Ridge (aka Champion) 25 round mags have this feature. I have a couple but haven't used them yet. I noticed that they don't sit as firmly as the Remington mags in mag well and are a bit sloppy. Also (and probably related) my last shot hold open doesn't function with these.
The spring design is different (snail spring), so it'll be interesting to see how they perform.
There's a thread about these mags floating around this forum somewhere...