For the Really, Really POD....

Why settle for a rabidly modern lace mantilla? Now you can cover your head with a
barbette,
linen or
silk veil, or a
reeeal wimple. Accessorize with a turret hat and be as beautiful as you are virtuous, you Tower of Ivory, you!

For those who don't want lay wimples and do like armor, Sword Maiden assures us there really were such things as warrior nuns.

The Order of the Glorious St Mary was founded by Loderigo d’Andalo of Bologna in 1233. It was the first religious order to grant the title of `militissa’ to women...

In 1477AD, Abbess Renee de Bourbon raised an army in order to attack a renegade monastery in Paris. She was on a personal crusade to end the excesses of the monasteries and convents under her domain. When she eventually prevailed, she made each nun and monk sign an oath of loyalty to her...

The problem of warrior nuns became so pervasive that in 15th century Bologna a law forbade citizens from loitering near convents for their own protection! Various popes established decrees forbidding women from engaging in martial combat or wearing armor, again in an effort to reduce the power of these warrior nuns. This is one of the decrees which were used against Joan d’ Arc.

Definitely check out Chivalry Today, particularly the essay on "The Road to Abu Ghraib".