Associated ball cups are $5 for 14, and it takes me all season to wear mine out. But if you insist, you can get the shock end hardware from X-ray that a lot of people use (appearantly). You'll wind up installing a long set screw where the ball stud mounts, and the captured ball in the shock end screws down onto it...
Speed Merchant Rev7, Tekin, TQ Racing (wire), Team Tamale
RC Excitement - Buy where you race, support your local tracks.