I would most definitely not buy genuine toyota parts, it's just too expensive, I can't give a quote, but parts from some kind of aftermarket supplier would be way cheaper, and probably of similar quality - depending how much you are willing to part with.
A copper head gasket isn't that expensive, probably under $200 from some place like Ridgecrest (?) and they are pretty good quality, my dad/bro use one in their rally car.