Seeing as gaboons, and all other vipers for that matter, are illegal in Washington state as of a few years ago (check out the herp law section on this website), I don't think many people will be willing to provide you with the species you seek. You have a few real options here though A) move to Oregon, B) acquire a gabby from someone in state who had it before the ban and has record of this, or C) acquire one illegally. Obviously I cannot recommend circumventing laws, however misguided they may be, so I personally would go with option A. Please think these options through before you acquire a snake, and remember, the state of Washington considers a venomoid snake to be exactly the same as a hot one.