Just an FYI, I obtained one on ebay a few years back, a new 1944 HS.
The 03 board on jouster.com is a good source for all things 03.
Sarco may have them.
Krieger makes a NM barrel for the '03 and this guy may have them:
Finally, I would like to recommend Dan Cowen, who did an 03 buildup for me. Riflesmith in Renton, WA is an 03 nut - 425-227-9280