I've been shooting some 6X7 so I need a 6x7 negative carrier for my beseller 23c III. Let me know what you have, with glass would be cool but without is fine too.
I have a 6x6 if you want to take the "file" route.
Also, Omega B carriers may fit. I have one (6x9) and it almost fits my 23c Dichro head. It will need a bit of filing on the hinge tab to seat properly. It does seat properly in the other direction, but you get vignetting as the head does not produce light evenly across a 9cm area in both directions. It might fit a condenser head without filing.
I don't think they made a 6x7 glass carrier. You would need to buy the universal glass carrier that goes to 6x9. Either use it as is or mask it to 6x7. That carrier is pretty common. I use a glassless 6x9 carrier for 6x7 because I like to see the edges. I don't mask the carrier and haven't seen any problems with edge flare.