Mobile Json Implementation

I posted this several days ago in the CF newsgroup, but noone replied.
I'm hoping I'll get a response here.

I've recently begun using Json to transmit data in my projects instead
of XML. I've been using the Newtonsoft.Json implementation and have
been very happy with the performance and ease of use. I've run into a
snag now, because I'm using CE5.0 based devices to contact our
services. Unfortunately, I haven't been able to locate good
implementation of a Json serializer/deserializer that will work on
mobile platforms. I've googled, but only have been able to find
non-mobile based implementations, and I don't really want to spend the
time to write my own implementation if one already exists.

Does anyone know of and can recommend a Json implementation that will
work on mobile devices?

thanks,

John