Ian,

The actual balls for the ball bearings are readily available.  They are a standard part. Mine were all in good shape, and got reassembled or I would measure them.  Measure carefully, and do not assume they are metric.  Many European manufacturers of moving rigging parts use 0.25 inch ball bearings. The cir-clips are also a standard size and widely available.  The plugs... of course not so much! 

I just had my swivel rebuilt.  The first cir-clip came out without a hitch, followed by the plug.  The second clip shattered when it was being removed, and left little corroded pieces of itself behind that made removing the plug a nightmare.  The cir-clips were replaced with stainless ones that will not have this problem.  

Like so many things, this is a compromise.  A higher risk of corrosion to the swivel body, but a lower risk of corrosion to an aluminum clip that can cause loss of the clips and plugs.  I have put a good coat of Lanocoat over the clips, and added the part to my routine inspection list.  Hopefully that, along with the part's location well above the normal salt spray zone, will keep things together and running smoothly.

An interesting piece of recent technical advice from Harkin about these plastic ball bearings in other applications.  They strongly suggest NOT lubricating them with the standard dry silicone lubricants-just keep them flushed with fresh water. The rational is the silicones can make the bearing race so slick that the balls start to slide instead of roll.  Then they get a flat spot, and things go down hill from there.  This was news to me, although it has the sound of truth to it.  

I haven't decided yet if I will stop putting dry lube on parts like this.  

Bill Kinney

SM160, Harmonie

Fort Lauderdale, FL, USA