Actually u can just buy it at the old merchant randomly but if u wanted the combination then its Small Barrel Bomb and Vespoid Wing. If you wanted the bounce bomb+, im not sure if its bomb arrowana or burst arrowana that u should combine it with. :scratch:
EDIT:
Wait thats jump not bounce, sorry. I also saw that on my cwcheat. i dont think its a real item or its just a hack but anyway try finding in the combo reference if there's an unknown item with barrel bomb or barrel lid as one of the ingridient of it