My good friend has issues with balance, and slipped a lot, so about two years ago we looked into studs etc. He tried basic sheet metal screws that you buy at the hardware supermarket. if you get the kind with a multidrive head format, they are pretty sharp, or a least sharp enough. What we found with his is that they pull out. each trip he was loosing one or two. Now he has hip boots, and i think we used a 3/8". if you could use something longer, maybe they wont pull out.
What i found works good for me, is something called Yaktrax. I had a pair because someone gave them to me. They are made for ice and snow traction. I never had enough of a problem to use them for that. They slip over your boot and have a velcro strap. They work real good, and my friend ended up getting a pair as well, after the last of his studs pulled out. The only downside I see to them, is that they are made from rubber. If you wade where the rocks have sharp edges, you can cut the rubber or wear it pretty quick. It happened on mine, but i fixed it up with some cord I had laying around.
Mine are in their second season, and I'll probably get three out of them. I think you can get them at Eastern Mountain Sports.