This question is the opposite of what is usually posted.
I dislike strap pins at the heel and wonder how to plug the hole left by the screw
Does the guitar have a heel cap which you could replace? Otherwise fill with a matching plug. Or a pearl dot?
what could be used for a matching plug-hard to find a dowel that thin
You'd have to cut your own plug. I'd be tempted to use pearl dot. Or make up a new heel cap? Depends how much time you want to put into it! Typically, Frank has a page about it: http://www.frets.com/FretsPages/Luthier/Technique/Guitar/Structural...
If it was in the heel cap I would use a pearl dot, however it is in the side of the heel the way Taylor Guitars mount theirs
anyone have a unspotted ebony bridge pin they no longer need?