here's what I have to offer....I have one for 6x7 and one for 6x6 (both for 120 size film). The attached photos show top and bottom of one carrier. You can see the 6x6 carrier to the looks the same - just different size hole.

These are both the newer style with the ring thingy on the bottom. The ring can be easily removed for compatibility with the older Omega D2 but, I think that your D6 is a newer style enlarger and likes the ring.

I'd be happy to trade one of these for a neg carrier for 6x4.5 (on 120 size film)...they made one for 6x4.5 on 127 that would be interesting but, not useful....but if you have the 4x4 on 127...that would be interesting and useful

anyway, I'm happy to sell either or both too of course. I have several other sizes too if you're interested.