Best answers I've heard or devised so far:
Leonhart's suggestion below. Probably the best rhetorical move Harry could possibly make.
Harry's portkey is transfigured into a tiny chip implanted under his own skin. It would be totally in character for him to do that.
If he has the range, transfigure long, thin tendrils that overlap with Voldemort and the death eaters' spinal cords at the neck level. Thin so that he doesn't have to work with as much mass/volume.
Transfigure the air around him into a carbon nanotube shell, buying himself time for another spell.
This is a new thread to discuss Eliezer Yudkowsky’s Harry Potter and the Methods of Rationality and anything related to it. This thread is intended for discussing chapter 113.
There is a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author’s Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.)
IMPORTANT -- From the end of chapter 113: