I don't think they would grow in you zone, they thrive best in zones 9 and up and still might have some problems in zones 9 and 10. If you are planning on keeping it in a greenhouse then you will probably get fruit within 4-6 years. As to where to get the tree, I would say graft a mature one onto cherimoya rootstock as they are compatible with it and that would flower in 1-2 yrs. For the scion-wood, I would try to contact some of the users on this forum who probably have some trees.
Regards-PM