Well, the Lake Pepin Tour guy does sell some neat 3-speed parts:

http://www.3speedtour.com/ (click on Parts)

Here's some white ribbed housing along with a gear cable:

http://cgi.ebay.com/Sturmey-Archer-H...e#ht_500wt_884

Here it is in "traditional" fluting:

http://cgi.ebay.com/Sturmey-Archer-1...6#ht_506wt_869

That seller, RetroBicycleSupply, often has lots of various 3-speed stuff: http://myworld.ebay.com/retrobicyclesupply/

Neal