Stainless steel sleeves to hold wire rope?
What you are doing appears to be similar to standard sailboat wire or cable "rails" and as such a visit to a boatyard/marine supplier would probably inform your process. Rather than being clamped at each post, the wires are typically tensioned from end to end (so the end-points need to be sturdy/strong.) They will also have crimp-sleeve (or swage-sleeve) fittings in stainless, but those are typically just at the ends (in your illustration, it would appear that you intend for them to be crimped inside the posts, which is impractical.)