Ah, there is more!
Joyeuse – traditionally thought to have been given to a part of Charlemagne’s personal sword. The name translates as “joyful”. Some legends claim that it was forged to contain the Lance of Longinus within its pommel; others state it was smithed from the same materials as Roland’s Durendal. It was believed to have its color change thirty times a day. There were many legends about Joyeuse to match those of Excalibur but the fact remains that the former one has actually been apparently identified and preserved (in parts) to our days.
Sharur, which means “smasher of thousands” is the weapon and mythic symbol of the god Ninurta. Sumerian mythic sources describe it as an enchanted talking mace. It has been suggested as a possible precursor for similar objects in other mythology such as Arthurian lore.Sharur has the power to fly across vast distances without impediment and communicate with its wielder and may take the form of a winged lion. Sharur plays a prominent role in an incident in which Ninurta is described as using it to defeat Asag, a monstrous demon. It provides crucial intelligence to the hero, acting as an emissary between the god Enlil and Ninurta and relating to him the former’s will, including a command to slay the architect Kur, a primeval serpent god venerated in Babylon, as well as a strategy to defeat Asag.
The Singing Sword is the primary weapon of the fictional character Prince Valiant, a Knight of the Round Table in the service of King Arthur. The Singing Sword’s first appearance in Prince Valiant lore came in the “Ilene Abducted” story, first published in 1938. In this story, the original owner of the sword is Prince Arn of Ord, Valiant’s rival for the beautiful maid Ilene. The two men put aside their differences when their beloved is kidnapped by Viking raiders. Arn lends Valiant the charmed sword so that he can hold off their pursuers while Arn rides ahead to free Ilene. The pair’s efforts prove futile; they discover she was killed in a shipwreck. Arn gives the Singing Sword to Valiant following this adventure, and the two part as friends. Later in the series, the Singing Sword is established as a sister to King Arthur’s Excalibur.
One of more obvious connections for Mulan carrying the sword would also be if it was the Sword of Attila the Hun, believed to be the sword of God and “of Mars supremacy in all wars” and reserved alone for Attila’s invincible arm.
As you can see, there are a lot of famous swords that could be attributed to that carried by Mulan, but a lot of them have some connections to Excalibur – they are either some country’s equivalent of the Arthurian sword or they are its siblings or even precursors. So as much as I would like her sword to be anything else but Excalibur, simply to avoid the obvious, perhaps it will end up being the sword of King Arhur, mainly because the show is aired in US so Excalibur would be known to most of the viewers there and would be the easiest to pick up on.
On another note, I even stumped onto a Malay equivalent of Excalibur, which is called Keris Taming Sari and is no more no less a dagger very closely resembling that of Rumple’s! 
It is said to possess magical powers. The keris was a prize from the Javanese kingdom of Majapahit to Hang Tuah after he fought and killed their supposedly invincible warrior named Taming Sari. The keris derives its name from the original owner.