Similarly, it would be seriously pushing it to rely on any scientific advances of the last (real-world) decade or so, unless there's a reason Harry would be able to at least semi-plausibly pre-discover them himself. Not that I can think of any of those which would help anyhow, but it's something to keep in mind.

Future tech - even things we think we could perhaps do - is probably right out. Harry could conceivably transfigure something (his epidermis, for example; has anybody mentioned that yet?) into a material that we know exists or could exist, and can describe in atomic or sub-atomic detail, yet can't synthesize; an arbitrary isotope of an arbitrary element should probably be possible, for example. He can't use transfiguration to produce something with negative mass (http://en.wikipedia.org/wiki/Negative_mass), though... at least, I would assume not, even if the science he knows suggests that such a thing is theoretically possible.