You could try Hatori USA just to see if they have any in stock:
www.hatoriusa.com
-OR-
You should be able to get a left hook header from Macs Products...You will probably have to call and ask them to make one for you...They only have .61 engines listed in the "special application" section of their website..I would assume they could do a .45 header too...
http://www.macspro.com/specialapp.asp
Congrats on the Aurora 45!! Please post some pictures of her!!!