Nancy-
Those are pretty tough to come by. I have been looking for them for awhile for a 10 gauge I inherited. Check ebay for brass. Sometimes a box of 25 sells, but you will probably pay a pretty penny for them. The other best place to look is the gun show. You never know what you will find there!
Best of Luck!
Kelsey
www.luvtohunt.com
High Mountain Hunting Supply