The 850R clutch you can still get new luckily, just bought 2 ironically last week.
1 for me and 1 for a friend.
:3 I get hounded for my lip from time to time, but considering they are NLA, ill keep it.
Most "rare" items here, you can get from the JPN market fairly readily which is nice.
Unfortunately you're after something that most people have probably either lost in their pile of parts, or scrapped with their car at some point.
I would 100% definitely try the facebook groups.