Ebay is a big gamble. I've spent over $400 on getting O Shamo eggs from there... Still don't have any O Shamo chicks. I would continue to search here or on craigslist for someone local.
Cackle is a choice, but if you want birds breed to Standard, do not order from a hatchery. We got 17 ducks from them. They are all "great" but not SOP great. Just great pets.
There are a few dedicated Orpington threads here. Maybe stop by a couple and ask if anyone there has eggs available. This is a good section to see whats available, but not always good for ISO type posts.