Nice set.
Yes the 2V lead acid accumulator can be replaced by a Cyclon or similar.
https://batterygroup.co.uk/Batteries...battery-E-cell
The HT battery can be made up by series connecting a load of PP3's (you will probably need 15 or 16 assuming the HT is 120V and use a lower tap as necessary for the detector.
And the Grid Bias Battery can be made up from 6 series connected AAA batteries as you will need to select a suitable tap.
Make them up into suitable scanned cases and they will look the business
Cheers
Mike T