What could Harry use to get out of this pickle?

• His mind, obviously, especially since negotiation is a possible action.
• Wandless magic? (Presumably learned from Bacon's diary.) Probably not anything requiring lots of magical power, but recall from the Azkaban arc that he could dispel his own magic almost effortlessly even back then. Now that he finds second-year spells easy, he just might be able to wandlessly manage that or other spells requiring very little magical power, such as Somnium, Innervate, and the TPC. Or possibly very small transfigurations (like a millionth of a gram of botulinium toxin), since he's had so much practice with that branch of magic.
• Anything he's already transfigured and is carrying with him. Sulphuric acid chips?
• His control over Dementors, which he doesn't need spells for.
• Ritual magic? He may not need a wand to perform a ritual.
• Possibly a backup wand / Time-Turner / other useful device?
• Mastery over his Cloak? He didn't give it to anyone as a possession.
• Mastery / ownership of other objects? Perhaps the Philosopher's Stone also has an "owner" property?
• Summoning a phoenix? Even if he can't get a phoenix of his own, he may be able to call one to aid him in a selfless act of heroism.
• Plans (for help or otherwise) already set in motion? Someone might look for him at the Quidditch game (probably as part of the debate about the Snitch), realize that he's not there despite setting up the banner and being interested in the outcome of the debate, and go look for him. Or maybe he's hidden someone in his pouch, or told Cedric about what he's doing. Or due to the Bayesian Conspiracy, Draco will realize that he's been Obliviated and help Harry.

I've probably missed something, so feel free to add more in the replies.