I always use Anco winter blades year round and they are great, and have metal attachment brackets. I agree, sometimes they are hard to find. Napa sells a winter blade that looks the same and seems pretty good, though the brackets are plastic. I have a set on right now. Kmart sells a winter blade too that isnt worth a penny, the cheap plastic crumbled when I tried to install them.
The only problem I have had is because the blades are taller, they ride up onto the wiper stop blocks on the car, and eventually develop an unwiped strip in the middle. That was solved by removing the stop blocks and filing them down square.