Same site you linked a complete head from has full valve kits. I just ordered one a few days ago because I sacrificed the valves my head came with after I found flaws in the seating surface. The whole kit is cheap enough that it makes it worth buying. Can't beat having spare everythings (valve stem seals, extra shims, etc). Just measure those stems and order accordingly. Quality is on par with factory at least.
5.5mm valve stem.
http://www.motopartsmax.com/index.ph...h/21_132/eID/8
6.5mm valve stem.
http://www.motopartsmax.com/index.ph...h/21_132/eID/8