Must admit I've never started crafting in Gondamon. I usually do it in Thorin's Hall or at Celondim if I'm in Ered Luin. If Áfast, the Supplier at Gondamon, doesn't have a ring then that's possibly a bug. You could try going to Thorin's Hall and see if Hatt the Supplier in the Maker's Hall (the room before the one with all the forges) has one.