The Plugable UGA-4KDP (DL-5500 chipset) was announced this week. It's shipping to USA addresses now, and to UK, EU, Canada, and Japan within 2 weeks.
http://plugable.com/products/uga-4kdp/
If you're in a geography that's not currently served, just email
support@plugable.com and we can notify you when units are on sale, and provide link. We're also happy to answer any questions.
A video showing the adapter in action:
https://www.youtube.com/watch?v=WFIte_SkgkM
Best regards,
Bernie