Title says it all.

I am using a roll cage that also ties into the same points, so a bar with an adjustable width would be nice...

we get ours from stable energies in NJ

I thought most cages had a bar specifically to attach the harness to. Maybe you could add one if yours does not.

I have never seen an adjustable width harness guide bar.

ioport.com or ioportracing.com has adjustable width ones....