I use proprietary "wired', (has a positive and a negative wire connected for charging purposes) battery holders which you should be able to buy similar locally.
These battery holders are available in units of 1, 2, 4, 6, cells etc and in AA, C or D sizes also.
If I have five cells use a 4+1=5 cells just remember to connect the two holders in series.
The charger auto detects the voltage, in this example 6 volts.
For your application buy a six cell "C" holder.
The one in the photo is "AA" size.