Steve’s thoughtfull details regarding the use of shaft collars as bearing housings lead me on a search for a supplyer. Bellow is a link to one. The 38mm inside diameter aluminium collars are one hole saw plunge away from being bearing brackets. Adds $30 to production costs, but eliminates a major fabrication step… might be effective for a one off.
“Who’s the well machined collar that can hold you tight?” - “Shaft!”
-Christopher
or you could just use the 40mm ones they advertise 
But then you wouldn’t have a lip on one side of the bearing holder to help hold the bearing in place.
It looks like my DM Vortex frame uses a similar shaft collar for its bearing holder. But DM machines out the inside so there is a lip on both sides of the bearing rather than just one lip on one side.
You’ze da Man, Childs. 
I got to juggling the link and fat brained it when looking up the Shaft lyrics. Thanx!
-C