Videomaker – Learn video production and editing, camera reviews › Forums › General › Capturing Video to a Memory Card › I have friends who used to
I have friends who used to own that camera and I don't think there's any way of doing what you want to do.
You can try posting this question on the JVC users forum at
http://www.dvinfo.net/forum/jvc-gy-hd-series-camera-systems/ and see if any users there have suggestions for you.
JVC did make the MR-HD100, a 100 GB. hard disk recorder for that camera.
There's also the Focus Enhancements Firestore FS-4 Pro HD hard disk recorder.
Neither of these are made any longer so Ebay is your only resort.