-
Also interested but struggling to find a set of second hand omegas
If you can't afford new brakes, you probably can't afford a customised after-market back plate :)
My advice would be to get OG Omegas if you can, preferably with the roller cam follower upgrade. If you get an X, consider whether your stem would tolerate being drilled to act as a cable stop and use the stopless back plate. It's what CX racers did back in the olden days
and some of them still do
An OG Omega :)
Pushed somebody off this afternoon who had the same compatibility issue (Omega X + OG P2/P3) that you, Nutshell and @Sainsburys_Ed are suffering from. If there are enough others out there who want to tackle it seriously, it's probably fixable :)