Can't provide you cost estimate I'm afraid, but some things you'll need to do...
1) Replace transmission with 2 electric motors. (the original Honda Hybrid used Honda inline IMA, not parallel Hybrid system).
2) Replace NiMH hybrid battery with a L-ION hybrid battery. NiMH will take up to 2 days to charge, not at all practical.
3) With all new electric motors and new L-Ion battery, you'll need an entirely new software system to handle hand-off between Engine and Electric.
In short, the power train and hybrid battery pack of the original Honda Hybrid is just not designed for this.
If you have a 2014 Honda Accord Hybrid, this would likely be a much simpler effort. Just increase the battery capacity and install charging circuit. Minor parameter modifications to the car software.