Go to Cabela's on line site..
http://www.cabelas.com/cabelas/en/templates/index/index-display.jhtml?id=cat20815&navAction=jump&n avCount=13&parentId=cat20712&parentType=ca tegory&rid=&_DARGS=%2Fcabelas%2Fen%2Fcommo n%2Fcatalog%2Fcategory-link.jhtml_A&_DAV=MainCatcat20712
Go into the black powder section and then over to the bullets and sabot section of their on line catalog. Look for a HORNADY XTP BULLETS. You might want to look into the 300 & 240 grain. I think the 240 grain would work good for you, but some rifles do like the 300 grain better.
You can also buy them in bulk and get them much cheaper in places like MidSouth Shooters supply. From some of the posts, they feel the .452 diameter is more accurate then the .430 diameter. You will need to buy some sabots if you get them in bulk. Be sure to match up the correct diameter sabot to the bullet.