Technetium has very similar properties with rhenium, but as its name says it must be made artificially, because due to its low lifetime all that has existed when the Solar System has been formed has disintegrated a long time ago.
Manganese has significantly different properties (due to smaller atomic size and greater electronegativity), so just substituting it in the same chemical formula would not create the same crystal structure and any properties would be different.
Nevertheless, it is likely that other substances with similar properties will be found, but it remains to be seen if any of them are stable enough and cheap enough to be used in practical devices.
