I placed a special order for a Gabrielle BB in natural calf leather (or barenia in H terms) with gold hardware a few months back, so as far as I am aware, Moynat is still taking special orders for Gabrielle. I did have to pay 20% extra as you've pointed out and also a deposit upfront. They are certainly pushing the new styles more, but my experience has been that as long as they have the materials for the combination you want, they will make it for you.
Please post a photo when it arrives! I fell in love with the Gabrielle (probably PM size since I’m not a mini bag girl) but don’t know what colour I want. I don’t have a tan/gold back either in my collection.