Looking for a specific old story. Help?

[macattack84]

Harry was in detention during a Hogwarts Masquerade Ball. Harry takes a potion to become a girl as part of his costume. He was Lady Guinevere and his soulmate was Lancelot (I think that's who they where at the party). Harry gave his soulmate a bracelet from his costume, so they could easily find each other later. In the end it was a Harry/Draco.

Help anyone? I read this year again and I’m trying again to find it.
Please and Thank you for any help.