odnt’ quote me without checking the schematic but yes it looks like a battery set, yes you could use some 9 volt cells at least temporarily. it might be 67 1/2 volt?
you could find that a printer powers supply could work. for example, I’m just getting rid of a Kodak one, they dont; make ink cartridges , its about 35 volts and Im unsure of the amperage, but maybe something similar could work? two of them together maybe?
you can probably download the graphics to make your own battery pack cover to make it look original , you could use rechargeable cells too. i guess it depends how often you see yourself or someone else using it. But it looks like you are on the right track. I’m sure Ive seen graphics for those battery packs around.
the connectors liike like 9V ones , but giant and if you do some searching Im sure there are some plans for building power supplies.