An arbor is a pretty basic turning project on the lathe. You can make it of brass or aluminum (though 4140HT, or 17-4PH, would be nicer), for all it matters, as the main purpose of having the parts hardened, seems to be to make it proof against the wage gorillas, who work on the shop floor and don't particularly care about actually CARING for the tools they use!I paid $2700 for a used Narex about 10 years ago. I would happily do it again. If you have used the 100 dollar chinese boring bars, this is so far superior and accurate that there is no comparison. It came with an R8 arbor, and when I switched to the Lagun CAT40 spindle I had to cobble something together as the CAT arbor is between 5-6 hundred...so I'm in the market for an arbor yet.
Besides, nothing will make one suddenly appear in your scope, quite like having just made your own part! LOL!