What about a Savoyard?
Unfortunately, besides being Catholic, they're rather short on candidates. Of all the Savoy princes they managed to produce one son between them, Charles Albert who only has 2 sons the youngest of which is only 10 and really can't be spared at this point
At this point, you really need a German or Scandinavian nobody who has some odd connections to great powers, and at this point, Scandinavia is out due to Denmark's succession crisis and Sweden being run by Bernadotte.
Maybe have Wilhelm of Schleswig Holstein and have him take the throne of Greece (he's 16 at this point) and marry Maria Nikloaevna, and have him gain more connections after little brother Christian becomes King of Denmark