Canon Unit V-2 in original leather case with Baseless Adapters PH and AG.
This flash uses an Eveready 505 carbon zinc battery or its equivalent (Neda 221 type). These are still available. Do a search on the 'net or on eBay. However, be aware that this is what is known as a "B-C" or battery-capacitor bulb flash. In addition to the 22.5v battery, there is a replaceable electrolytic capacitor that's roughly the size of a AA battery. Make sure that the battery and capacitor are inserted in the correct locations. Over the years, the capacitor can deteriorate to the point where it will not hold a sufficient charge to fire the flash bulb, even with a good battery.
Instruction manual can be found here: