Kent still makes their Tungsten Matrix, which is safe to use in older guns. However, that stuff has some serious velocity and chamber pressures may be brutal. I haven't found tungsten matrix as a reloading component but I have found Bismuth. Last time I bought Bismuth to reload with was at Cabelas the price was $72 for 7 lbs of it.
I'll tell you guys I've had enough. I went out and purchased a single barrel 10 gauge from New England Arms and just use that for waterfowl. If I was a better shot I would have purchased Ruger's sweet little 28 gauge but whatever
All the best