Horsea, the ones I currently have are made by Metalab. You can also get them made by Stateline Tack. I've had both, and they're both very well made.
I LOVE jointed stirrups, and don't ever plan to go back to hard irons.
They make it so I can ride for hours now without having to pay the price by pain in my ankles and knees, like the hard irons.
Just make sure you go one size up from your regular irons, so your foot can clear the rubber joint covering. I get the 4.75" when I buy jointed, because I always used 4.5" in hard.
Where's the starry-eyed love emoticon? That's how much I love my jointed stirrups!
Here's a website where you can find them: http://www.thefind.com/sports/info-jointed-irons
Trust me, once you go jointed you'll never want to ride in a hard iron again!