I am pretty sure that I have a MKI barrel in one of my 'bits' ammo boxes in the garage - I think it is a pre-war one though.
As I am currently taking a break from packing to catch an early flight tomorrow to Italy I ain't going digging at the moment. I'm only away for a week so if you want the barrel (assuming I am right and it is there - pretty sure) email me during the week to remind me and I will dig it out when I get back.
It'll be a freeby.