I emailed ProClip a few weeks back and asked when the C would have a clip. Just got an email from them today saying it was ready to order. http://www.proclipusa.com/854784.aspx
Install instructions: http://www.proclipusa.net/media/documents/instructions/854784.pdf Looks like you need the mount (From original post) and a device holder to make it all work. Total comes to $69 for an iPhone holder and C mount.
I got the same email and ordered mine today. $64.98 to hold the Nokia N8. I have no worries since the product has a great reviews from Nokia users.
I found a bit of plastic in my garage, painted it black with some left-over paint and stuck on a a few pieces of 3m dual lock. Moumted the plastic to the dash in front of the vent with its base resting on the little ledge at the base of said vent. Then mounted my el cheapo nav to the plastic. Total cost ... less than a dollar. (Not counting the nuvi.)
just ordered one. just the mounting clip. and a cheapo garmin mount from amazon Amazon.com: ARKON APGN-VSM Vehicle Specific Mount Adapter Plate Connects 4 Hole AMPS VSM to Garmin Nuvi 17mm: GPS & Navigation