Take the old one with you when you go to purchase a new turnbuckle. You may be able to find a close match. To find an original type, however, I think you need to attend the next marine flea market . There's really no downside to using a different model of turnbuckle. In fact, I've seen a number of boats with mismatched turnbuckles. Why not start your your upgrade one turnbuckle at a time . .