The only person I know of who could supply them is under the quarantine zone, and her packages do travel through the qz during transit. Out of biosecurity, I won't recommend.
I have 8 d'Uccle eggs currently, plus lots of Japanese/Serama project eggs but full disclosure I'm not sure how old each...
I know you're also fighting a losing battle with your lone d'Uccle chick. As it is, I'd suggest focusing on what may be wrong in the rearing of your young chicks before getting more. Do you already have an incubator on hand?
How many eggs are you looking for? Eggs from show quality, breeder quality, or pet quality stock? I have eggs, but only 6 and from one pair so probably not a great option.