'K, all, here's an update. I went ahead with my bolt idea for now. It's a gradually rounded top, not hex -- imagine something like a flattened toadstool. First sanded the lettering down and to rough up the surface, then primed with rust-inhibiting primer (should give me a little more time between replacements) and then sprayed with the paint. It doesn't look too bad at all, and the whole thing only cost me $.045. Works for me!