Hi,
Nice pics that really help explain what you are trying to do, and i presume you did not use a 100 year only camera to take those shots
First thought:
Donate that flashlight to a museum, buy a new XML LED type LED flashlight and associated Li-in batteries. It will be so bright it will amaze and confuse you.
Second thought:
If you still want to get this old thing going, try to get at the bulb itself. It should be replaceable so you should be able to take it out and find the part number. If so, we can look up the part number and find out what kind of voltages it can take.
Third thought:
If you incorporate a small buck converter circuit into your 'new' battery pack, you will be able to use a standard 12v lead acid battery which you can get almost anywhere on the web these days. The buck circuit can be adjusted to exactly 9v if that's what you prefer, or even less, 8.5v, if you really want to be safe. The buck modules are available on sites like Amazon for example.
Forth thought:
A battery holder that holds 6xAA cells will give about 9v, so a bunch of them in parallel might do it?
If you are after a bright light though the new XML LED flashlight will be the best choice here, and you can still try to fix the old one if you like.