eBay is where I'd start. Someone's spare parts pile is probably where I'd finish. Lots of D15 engines should be occupying space in people's garages everywhere, because lots of people have swapped their civics already. You might get lucky and find someone near you. Ask kids in parking lots that hang out late-night with their ricemobiles, and one of them might know somebody. Some people would give them away just to get rid of them. Heck, I've got a 8-valve CX head in my garage. You probably don't want it... I definitely don't want to ship it.