Bonk 3 is one of the rarer games in the PC Genjin series. Now you can get the original version where Bonk transforms into a cavewoman for 600 yen ($6.50). The co-op mode works too, but only if you play Bonk 3 on a PlayStation 3.
Alternatively, you can get The Kung Fu aka China Warrior outside of Japan, but do you really want that over Bonk?
Bonk 3: Bonk’s Big Adventure