We could build you one it is very straight fowardI live in Tallahassee Forida and bamboo is easy to get river cane works or you could order bamboo from me. tuning is a matter of adjusting the length untill you arrive at the tone you are after.
I use a little toy keyboard as a standard. As far as your zampona check it to see how well in tune it is that will affect the quality of your playing.
bending down to a half step is the only way to go with the pipes there is no reaching up.