Mud hole
http://www.mudhole.com/Shop-Our-Catalog/REC-Components

Or direct from REC
http://www.reelseats.com/catalog/ind...1b446c4e209cb7

They both sell cork rings and finished handles
REC http://www.reelseats.com/catalog/ind...1b446c4e209cb7

Mud hole
http://www.mudhole.com/Shop-Our-Catalog/Cork-Rings_2
http://www.mudhole.com/Shop-Our-Catalog/Cork

Probably a dozen other decent rod building supply web sites out there as well. These are my 2 favorites.

As for the rod sock and tube? just about EVERY fly fishing and rod building site sells them. Just a matter of what price range you want.