I think you are out off luck getting a 6x9 carrier for any B series Omega, they are 6x6 machines. You need to upgrade to a C or D series to enlarge 6x9 negatives, or get a Beseler 23C series machine. Omega series designation is A for 35mm, B for up to 6x6 (21/4 sq), C up to 6x9, D up to 4x5, E up to 5x7.
I have an omega B8, which handles up to 6x9. I have found them for ~$20-25 on ebay, wanting to see if anyone on here has one they don’t need and would make a better offer.