The D15Z1 should not be too hard to find, though they are pretty old now. Try
Car-Part.com - Used Auto Parts Market ... but just buying the engine without the wire harness, ECU, and wideband O2 would not be wise... no lean burn, poor functioning in general without all those critical parts. How about using a D16Y5 instead? More recent. It's OBD2. And it has a little more HP the the fifth gen fuel-sipper engines. It can be mater to a VX/CX transmission too if the already tall gearing that comes with its stock transmission is still not tall enough for your project.