Not sure what stainless you have, may harden if you heat it and quench, or anneal if you heat and cool in air.
I machined a lump of bms bar to the id of the tube with a step up to the od of the tube further down it. Put them in a small press and it's done.
I assume you are trying to make slider joints on ss tube?
yes. Just seen this, then saw the price are they being ironic with the ebay username? http://www.ebay.co.uk/itm/ETL3-EXHA...540?pt=LH_DefaultDomain_3&hash=item3a8074254c
I doubt they sell many as you say, not hard to turn on a lathe. I will ask local machine shop i think.
Hardly expensive, when you consider the metal, time and other costs required to make it. I'd be surprised if a machinist would bother knocking one out for much less, if at all.
A chinese machinist would make you one for a fiver....