From what I've experienced with gen and rep Navi's, and swapping bracelets, is that the end links are profiled on the case side to match that particular case. So a Navitimer of 20yrs vintage may not have exactly the same case profile as the rep.
However, if you know what you're doing, you could gently reprofile the rep end links?
Or if they are loose, a tiny bit of hot glue will conform as you press the end link in. Sounds a bit amateur, but it's easily removed....