If you are interested, I found 2 complete engines. a 2006 for $750 and a 2007 for $800 + $100 shipping from Kentucky. Or if you are interested in rebuilding, a complete lower end for $475 free shipping from Missouri, and a set of cases for $175 free shipping from Penn., but you would have to get a new crankshaft from Honda for about $270.00
Using used parts, the motor could probably be rebuilt for $850 with the only guarantee being against defective parts. Keep in mind that these motors are push-rod valve train motors. They are considered utility
perfromance engines. I'm guessing your motor exploded due to high RPM use. If you are trying to run this machine on a track, I would recommend salvaging it and getting a sport model that is more suited to the way you are using it.