Greg,

I just thought of a possible source you might check for an original 1903A3 bolt. Bill Ricca is a trusted member of this site and he may have what you need on hand.
You'll need to call or email him to check for availability. Contact info is on his site.

Here's a link to his 1903 parts page - Bill Ricca's 03/03A3 Parts and Accessories

HTH,
~ Harlan