Help! What screw can replace Colt 1860 shoulder stock screw?

I have a Colt 2nd gen 1860 - a great gun, but the shoulder stock screws stick out too far for comfort, and I don't use a stock anyway. What screw can I use as a replacement that fits flush to the frame. Thanks for any and all opinions/advice/comments.
"Bloody Bill"
 
I found a 1/4" black plastic screwdriver tweaker used for electronic adjustments and made two screws for my 1860. Screw the rod into the holes to cut threads on it. Then cut the threaded section off and screw into the frame. Mine has been like this for years.

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Metric M4 appears to be not very far away, at least for a limited length of thread engagement.
But I wish I knew what the proper thread was. Not enough on there to measure it properly.
 
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