I studied with Jeffrey Hoffstein at Brown, one of the creators of NTRU. He told me recently NTRU, which is lattice based, is one of the few (only?) NIST-recommended QC-resistant algorithms.
We talked over layering on NTRU to Bitcoin last year when I was out that way; I think such a thing could be done relatively easily from a crypto standpoint. Of course, there are many, many more questions beyond just the crypto.