I don't know. Can you give me an online source?
I'm at a loss as to how one may fit a bearing, or lubricated bushing, on the water end of the tube. Won't it rust or dry out?
In my opinion the best materials to use are phosphor bronze or leaded bronze bushes, with stainless steel or bright drawn steel shaft. High quality ss will not rust, bright drawn may do in time. Also, bronze, and in particular leaded bronze is to some extent, self lubricating in water.
I think some manufacturers use brass for bushes, its ok but not as good as bronze and will need a little lubrication.
If you are concerned about oil/grease getting into the water, mass produced bought in shafts do not have the tight tolerances that can be achieved with one offs, so, if you know someone with a lathe - thats the best way to go.
For your interest, I have used bronze bushes for years, never had to replace one and VERY occasionally add only a little light oil for lubricant .
Ian
PS. Others might not agree with my comments, but they work fine for me.