Mandarin eggs can't be found on eBay at about 60$ for just two eggs. It's not worth it. Maybe if you have an rcom incubator but even if you do it's still not worth it. Ornamental ducklings are not sold. Universal rule kinda.
I second everything cajunfowl0 said. Your best bet is getting on a waiting list for a 2016 hatch Mandarin Duck pair. My website is www.bluecreekaviaries.com.